storage/engine: introduce a datadriven framework to run MVCC tests

Previously MVCC tests were hand-coded in Go.
This was making it hard(er) to introduce new tests or modify existing
tests.

This commit improves upon this situation by introducing a new
datadriven test, `TestMVCCHistories`, which runs MVCC
tests written using a DSL:

```
begin_txn      t=<name> [ts=<int>[,<int>]]
remove_txn     t=<name>
resolve_intent t=<name> k=<key> [status=<txnstatus>]
restart_txn    t=<name>
update_txn     t=<name> t2=<name>
step_txn       t=<name> [n=<int>]
advance_txn    t=<name> ts=<int>[,<int>]
txn_status     t=<name> status=<txnstatus>

check_intent   k=<key> [none]

put       [t=<name>] [ts=<int>[,<int>]] [resolve] k=<key> v=<string> [raw]
cput      [t=<name>] [ts=<int>[,<int>]] [resolve] k=<key> v=<string> [raw] [cond=<string>]
increment [t=<name>] [ts=<int>[,<int>]] [resolve] k=<key> [inc=<val>]
del       [t=<name>] [ts=<int>[,<int>]] [resolve] k=<key>
get       [t=<name>] [ts=<int>[,<int>]] [resolve] k=<key> [inconsistent] [tombstones]
scan      [t=<name>] [ts=<int>[,<int>]] [resolve] k=<key> [end=<key>] [inconsistent] [tombstones] [reverse]

merge     [ts=<int>[,<int>]] k=<key> v=<string> [raw]

clear_range    k=<key> end=<key>
```

Where `<key>` can be a simple string, or a string
prefixed by the following characters:

- `=foo` means exactly key `foo`
- `+foo` means `Key(foo).Next()`
- `-foo` means `Key(foo).PrefixEnd()`

Additionally, the pseudo-command `with` enables sharing
a group of arguments between multiple commands, for example:

```
with t=A
   begin_txn
   with k=a
     put v=b
     resolve_intent
```

Release note: None

pkg/storage/engine/testdata/mvcc_histories/clear_range

@@ -0,0 +1,64 @@
+
+# Populate some values
+
+run ok
+with t=A v=abc resolve
+  begin_txn ts=44
+  put  k=a
+  put  k=a/123
+  put  k=b
+  put  k=b/123
+  put  k=c
+----
+>> at end:
+txn: "A" meta={id=00000000 key=/Min pri=0.00000000 epo=0 ts=0.000000044,0 min=0.000000000,0 seq=0} rw=true stat=PENDING orig=0.000000044,0 max=0.000000000,0 rts=0.000000000,0 wto=false
+data: "a"/0.000000044,0 -> /BYTES/abc
+data: "a/123"/0.000000044,0 -> /BYTES/abc
+data: "b"/0.000000044,0 -> /BYTES/abc
+data: "b/123"/0.000000044,0 -> /BYTES/abc
+data: "c"/0.000000044,0 -> /BYTES/abc
+
+
+run ok
+clear_range k=a end=+a
+----
+>> at end:
+data: "a/123"/0.000000044,0 -> /BYTES/abc
+data: "b"/0.000000044,0 -> /BYTES/abc
+data: "b/123"/0.000000044,0 -> /BYTES/abc
+data: "c"/0.000000044,0 -> /BYTES/abc
+
+run ok
+clear_range k=a end=-a
+----
+>> at end:
+data: "b"/0.000000044,0 -> /BYTES/abc
+data: "b/123"/0.000000044,0 -> /BYTES/abc
+data: "c"/0.000000044,0 -> /BYTES/abc
+
+run ok
+clear_range k=a end==b
+----
+>> at end:
+data: "b"/0.000000044,0 -> /BYTES/abc
+data: "b/123"/0.000000044,0 -> /BYTES/abc
+data: "c"/0.000000044,0 -> /BYTES/abc
+
+run ok
+clear_range k=a end=+b
+----
+>> at end:
+data: "b/123"/0.000000044,0 -> /BYTES/abc
+data: "c"/0.000000044,0 -> /BYTES/abc
+
+run ok
+clear_range k=a end=-b
+----
+>> at end:
+data: "c"/0.000000044,0 -> /BYTES/abc
+
+run ok
+clear_range k=a end=-c
+----
+>> at end:
+<no data>

pkg/storage/engine/testdata/mvcc_histories/conditional_put

@@ -0,0 +1,113 @@
+run error
+cput k=k v=v cond=v2 ts=123
+----
+>> at end:
+<no data>
+error: (*roachpb.ConditionFailedError:) unexpected value: <nil>
+
+# Verify the difference between missing value and empty value.
+
+run error
+cput k=k v=v cond= ts=123,1
+----
+>> at end:
+<no data>
+error: (*roachpb.ConditionFailedError:) unexpected value: <nil>
+
+# Do a conditional put with expectation that the value is completely missing; will succeed.
+
+run ok
+cput k=k v=v ts=123,2
+----
+>> at end:
+data: "k"/0.000000123,2 -> /BYTES/v
+
+# Another conditional put expecting value missing will fail, now that value1 is written.
+
+run error
+cput k=k v=v ts=123,3
+----
+>> at end:
+data: "k"/0.000000123,2 -> /BYTES/v
+error: (*roachpb.ConditionFailedError:) unexpected value: raw_bytes:"\000\000\000\000\003v" timestamp:<wall_time:123 logical:2 > 
+
+# Conditional put expecting wrong value2, will fail.
+
+run error
+cput k=k v=v cond=v2 ts=123,4
+----
+>> at end:
+data: "k"/0.000000123,2 -> /BYTES/v
+error: (*roachpb.ConditionFailedError:) unexpected value: raw_bytes:"\000\000\000\000\003v" timestamp:<wall_time:123 logical:2 > 
+
+# Move to an empty value. Will succeed.
+
+run ok
+cput k=k v= cond=v ts=123,5
+----
+>> at end:
+data: "k"/0.000000123,5 -> /BYTES/
+data: "k"/0.000000123,2 -> /BYTES/v
+
+# Move key2 (which does not exist) to from value1 to value2.
+# Expect it to fail since it does not exist with value1.
+
+run error
+cput k=k2 v=v2 cond=v ts=123,6
+----
+>> at end:
+data: "k"/0.000000123,5 -> /BYTES/
+data: "k"/0.000000123,2 -> /BYTES/v
+error: (*roachpb.ConditionFailedError:) unexpected value: <nil>
+
+# Move key2 (which does not yet exist) to from value1 to value2, but
+# allowing for it not existing.
+
+run ok
+cput k=k2 v=v2 cond=v ts=123,7 allow_missing
+----
+>> at end:
+data: "k"/0.000000123,5 -> /BYTES/
+data: "k"/0.000000123,2 -> /BYTES/v
+data: "k2"/0.000000123,7 -> /BYTES/v2
+
+# Try to move key2 (which has value2) from value1 to empty. Expect error.
+
+run error
+cput k=k2 v= cond=v allow_missing ts=123,8
+----
+>> at end:
+data: "k"/0.000000123,5 -> /BYTES/
+data: "k"/0.000000123,2 -> /BYTES/v
+data: "k2"/0.000000123,7 -> /BYTES/v2
+error: (*roachpb.ConditionFailedError:) unexpected value: raw_bytes:"\000\000\000\000\003v2" timestamp:<wall_time:123 logical:7 > 
+
+# Try to move key2 (which has value2) from value2 to empty. Expect success.
+
+run ok
+cput k=k2 v= cond=v2 allow_missing ts=123,9
+----
+>> at end:
+data: "k"/0.000000123,5 -> /BYTES/
+data: "k"/0.000000123,2 -> /BYTES/v
+data: "k2"/0.000000123,9 -> /BYTES/
+data: "k2"/0.000000123,7 -> /BYTES/v2
+
+# Now move to value2 from expected empty value.
+
+run ok
+cput k=k v=v2 cond= ts=123,10
+----
+>> at end:
+data: "k"/0.000000123,10 -> /BYTES/v2
+data: "k"/0.000000123,5 -> /BYTES/
+data: "k"/0.000000123,2 -> /BYTES/v
+data: "k2"/0.000000123,9 -> /BYTES/
+data: "k2"/0.000000123,7 -> /BYTES/v2
+
+# Verify we get value2 as expected.
+
+run ok
+get k=k ts=123,11
+----
+get: "k" -> /BYTES/v2

pkg/storage/engine/testdata/mvcc_histories/conditional_put_with_txn

@@ -0,0 +1,65 @@
+run ok
+begin_txn t=A ts=123
+----
+>> at end:
+txn: "A" meta={id=00000000 key=/Min pri=0.00000000 epo=0 ts=0.000000123,0 min=0.000000000,0 seq=0} rw=true stat=PENDING orig=0.000000123,0 max=0.000000000,0 rts=0.000000000,0 wto=false
+
+# Write value1.
+
+run ok
+with t=A
+  step_txn
+  cput k=k v=v
+----
+>> at end:
+txn: "A" meta={id=00000000 key=/Min pri=0.00000000 epo=0 ts=0.000000123,0 min=0.000000000,0 seq=1} rw=true stat=PENDING orig=0.000000123,0 max=0.000000000,0 rts=0.000000000,0 wto=false
+meta: "k"/0.000000000,0 -> txn={id=00000000 key=/Min pri=0.00000000 epo=0 ts=0.000000123,0 min=0.000000000,0 seq=1} ts=0.000000123,0 del=false klen=12 vlen=6
+data: "k"/0.000000123,0 -> /BYTES/v
+
+# Now, overwrite value1 with value2 from same txn; should see value1
+# as pre-existing value.
+
+run ok
+with t=A
+  step_txn
+  cput k=k v=v2 cond=v
+----
+>> at end:
+txn: "A" meta={id=00000000 key=/Min pri=0.00000000 epo=0 ts=0.000000123,0 min=0.000000000,0 seq=2} rw=true stat=PENDING orig=0.000000123,0 max=0.000000000,0 rts=0.000000000,0 wto=false
+meta: "k"/0.000000000,0 -> txn={id=00000000 key=/Min pri=0.00000000 epo=0 ts=0.000000123,0 min=0.000000000,0 seq=2} ts=0.000000123,0 del=false klen=12 vlen=7 ih={{1 /BYTES/v}}
+data: "k"/0.000000123,0 -> /BYTES/v2
+
+# Writing value3 from a new epoch should see nil again.
+
+run ok
+with t=A
+  restart_txn
+  step_txn
+  cput k=k v=v3
+----
+>> at end:
+txn: "A" meta={id=00000000 key=/Min pri=0.00000000 epo=1 ts=0.000000123,0 min=0.000000000,0 seq=1} rw=true stat=PENDING orig=0.000000123,0 max=0.000000000,0 rts=0.000000000,0 wto=false
+meta: "k"/0.000000000,0 -> txn={id=00000000 key=/Min pri=0.00000000 epo=1 ts=0.000000123,0 min=0.000000000,0 seq=1} ts=0.000000123,0 del=false klen=12 vlen=7
+data: "k"/0.000000123,0 -> /BYTES/v3
+
+# Commit value3 at a later timestamp.
+
+run ok
+with t=A
+  advance_txn    ts=124
+  resolve_intent k=k
+----
+>> at end:
+txn: "A" meta={id=00000000 key=/Min pri=0.00000000 epo=1 ts=0.000000124,0 min=0.000000000,0 seq=1} rw=true stat=PENDING orig=0.000000123,0 max=0.000000000,0 rts=0.000000000,0 wto=false
+data: "k"/0.000000124,0 -> /BYTES/v3
+
+# Write value4 with an old timestamp without txn...should get a write
+# too old error.
+
+run error
+cput k=k v=v4 cond=v3 ts=123
+----
+>> at end:
+data: "k"/0.000000124,1 -> /BYTES/v4
+data: "k"/0.000000124,0 -> /BYTES/v3
+error: (*roachpb.WriteTooOldError:) WriteTooOldError: write at timestamp 0.000000123,0 too old; wrote at 0.000000124,1

pkg/storage/engine/testdata/mvcc_histories/conditional_put_write_too_old

@@ -0,0 +1,52 @@
+# This test verifies the differing behavior
+# of conditional puts when writing with an older timestamp than the
+# existing write. If there's no transaction, the conditional put
+# should use the latest value. When there's a transaction, then it
+# should use the value at the specified timestamp.
+
+run ok
+put ts=10 k=k v=v1
+----
+>> at end:
+data: "k"/0.000000010,0 -> /BYTES/v1
+
+# Try a non-transactional put @t=1 with expectation of nil; should fail.
+run error
+cput ts=1 k=k v=v2
+----
+>> at end:
+data: "k"/0.000000010,0 -> /BYTES/v1
+error: (*roachpb.ConditionFailedError:) unexpected value: raw_bytes:"\000\000\000\000\003v1" timestamp:<wall_time:10 > 
+
+# Now do a non-transactional put @t=1 with expectation of value1; will "succeed" @t=10,1 with WriteTooOld.
+run error
+cput ts=1 k=k v=v2 cond=v1
+----
+>> at end:
+data: "k"/0.000000010,1 -> /BYTES/v2
+data: "k"/0.000000010,0 -> /BYTES/v1
+error: (*roachpb.WriteTooOldError:) WriteTooOldError: write at timestamp 0.000000001,0 too old; wrote at 0.000000010,1
+
+# Try a transactional put @t=1 with expectation of value2; should fail.
+run error
+with t=a
+  begin_txn ts=1
+  cput k=k v=v2 cond=v1
+----
+>> at end:
+txn: "a" meta={id=00000000 key=/Min pri=0.00000000 epo=0 ts=0.000000001,0 min=0.000000000,0 seq=0} rw=true stat=PENDING orig=0.000000001,0 max=0.000000000,0 rts=0.000000000,0 wto=false
+data: "k"/0.000000010,1 -> /BYTES/v2
+data: "k"/0.000000010,0 -> /BYTES/v1
+error: (*roachpb.ConditionFailedError:) unexpected value: <nil>
+
+# Now do a transactional put @t=1 with expectation of nil; will "succeed" @t=10,2 with WriteTooOld.
+run error
+with t=a
+  cput k=k v=v3
+----
+>> at end:
+meta: "k"/0.000000000,0 -> txn={id=00000000 key=/Min pri=0.00000000 epo=0 ts=0.000000001,0 min=0.000000000,0 seq=0} ts=0.000000010,2 del=false klen=12 vlen=7
+data: "k"/0.000000010,2 -> /BYTES/v3
+data: "k"/0.000000010,1 -> /BYTES/v2
+data: "k"/0.000000010,0 -> /BYTES/v1
+error: (*roachpb.WriteTooOldError:) WriteTooOldError: write at timestamp 0.000000001,0 too old; wrote at 0.000000010,2

pkg/storage/engine/testdata/mvcc_histories/deletes

@@ -0,0 +1,33 @@
+## A simple txn that deletes.
+## The delete tombstone is placed alongside the previous value, at the newer timestamp.
+
+run ok
+with t=A
+  begin_txn  ts=44
+  del   k=a resolve
+  remove_txn
+----
+>> at end:
+data: "a"/0.000000044,0 -> /<empty>
+
+# Show the value disappears from gets.
+
+run ok
+with t=A
+  begin_txn ts=45
+  get k=a
+  remove_txn
+----
+get: "a" -> <no data>
+>> at end:
+
+# Show the tombstone.
+
+run ok
+with t=A
+  begin_txn ts=45
+  get k=a tombstones
+  remove_txn
+----
+get: "a" -> /<empty>
+>> at end:

pkg/storage/engine/testdata/mvcc_histories/empty_key

@@ -0,0 +1,31 @@
+run error
+get ts=0,1 k=
+----
+error: (*errors.fundamental:) attempted access to empty key
+
+run error
+put ts=0,1 k= v=a
+----
+>> at end:
+<no data>
+error: (*errors.fundamental:) attempted access to empty key
+
+run ok
+scan ts=0,1 k= end=a
+----
+scan: /Min-"a" -> <no data>
+
+
+run error
+scan ts=0,1 k=a end=
+----
+error: (*errors.fundamental:) attempted access to empty key
+
+run error
+begin_txn t=A
+resolve_intent t=A k=
+----
+>> at end:
+txn: "A" meta={id=00000000 key=/Min pri=0.00000000 epo=0 ts=0.000000000,0 min=0.000000000,0 seq=0} rw=true stat=PENDING orig=0.000000000,0 max=0.000000000,0 rts=0.000000000,0 wto=false
+<no data>
+error: (*errors.fundamental:) attempted access to empty key

pkg/storage/engine/testdata/mvcc_histories/get_negative_timestamp

@@ -0,0 +1,18 @@
+run ok
+put k=k v=v ts=1
+----
+>> at end:
+data: "k"/0.000000001,0 -> /BYTES/v
+
+run error
+get k=k ts=-1
+----
+error: (*withstack.withStack:) cannot write to "k" at timestamp 0.-00000001,0
+
+
+run error
+put k=k v=v ts=-1
+----
+>> at end:
+data: "k"/0.000000001,0 -> /BYTES/v
+error: (*withstack.withStack:) cannot write to "k" at timestamp 0.-00000001,0