parser: adjust ALTER TENANT ALL syntax

[rafiss]

This change brings the syntax inline to what was proposed in the RFC.
This is worthwhile since it matches with the syntax we use in other
"ALL" cases -- notably `ALTER ROLE ALL SET ...``.

Release justification: low risk update to new functionality
Release note: None

[cockroach-teamcity]

This change is 

[knz]

nice, thanks

[ajstorm]

Fancy!

Reviewable status: complete! 1 of 0 LGTMs obtained

[rafiss]

seems like an unrelated flake

bors r=knz,ajstorm

[rafiss]

error was

[email protected]:26257/movr> \demo restart 3
node 3 has been restarted
[email protected]:26257/movr> select node_id, draining, decommissioning, membe �rship from crdb_internal.gossip_liveness ORDER BY node_id;
  node_id | draining | decommissioning | membership
----------+----------+-----------------+-------------
        1 |  false   |      false      | active
        2 |  false   |      false      | active
        3 |   true   |      false      | active
        4 |  false   |      false      | active
        5 |  false   |      false      | active
(5 rows)


Time: 1ms total (execution 1ms / network 0ms)

[email protected]:26257/movr> 
.220309 16:54:15.699234348 EXPECT TEST: TIMEOUT WAITING FOR "3 |  false   |      false      | active"
non-zero exit code: 1

this is captured in #76448

[craig]

Build succeeded:

• GitHub CI (Cockroach)