storage: support range keys in SSTWriter and sstIterator

[erikgrinaker]

We need to handle range keys in SSTs, e.g. for backup/restore and Raft snapshots. In order to do this, we need support for range keys in SSTWriter and sstIterator. This involves implementing the range key methods from the Writer and SimpleMVCCIterator interfaces such that they comply with the interface, and adding tests (iterator tests via TestMVCCHistories).

cockroach/pkg/storage/sst_writer.go

Lines 145 to 158 in 44f1ca7

	// ExperimentalPutMVCCRangeKey implements the Writer interface.
	func (fw *SSTWriter) ExperimentalPutMVCCRangeKey(MVCCRangeKey, MVCCValue) error {
	panic("not implemented")
	}
	// ExperimentalClearMVCCRangeKey implements the Writer interface.
	func (fw *SSTWriter) ExperimentalClearMVCCRangeKey(MVCCRangeKey) error {
	panic("not implemented")
	}
	// ExperimentalClearAllMVCCRangeKeys implements the Writer interface.
	func (fw *SSTWriter) ExperimentalClearAllMVCCRangeKeys(roachpb.Key, roachpb.Key) error {
	panic("not implemented")
	}

cockroach/pkg/storage/sst_iterator.go

Lines 175 to 188 in 44f1ca7

	// HasPointAndRange implements SimpleMVCCIterator.
	func (r *sstIterator) HasPointAndRange() (bool, bool) {
	panic("not implemented")
	}
	// RangeBounds implements SimpleMVCCIterator.
	func (r *sstIterator) RangeBounds() roachpb.Span {
	panic("not implemented")
	}
	// RangeKeys implements SimpleMVCCIterator.
	func (r *sstIterator) RangeKeys() []MVCCRangeKeyValue {
	panic("not implemented")
	}

Jira issue: CRDB-16532

Epic CRDB-2624

[blathers-crl]

cc @cockroachdb/replication