clusterversion,kvserver,sql: remove AutoStatsTableSettings

[celiala]

This commit removes the 22.1 AutoStatsTableSettings version gate.

Cleanup was done following guidance from 21.2 cleanup:

For the most part, if the gates were just simple if !version.IsActive { return x } or something, I just removed the block, and even if it was a little more complicated, like args = [x]; if version { args = append(args, y) }; foo(args) I still tried to mostly inline it such that it looked natural (i.e. remove that append and make it args = [x, y]).

However for just a couple more complicated cases that were referring to <21.2 versions that needed to be replaced when those were deleted, I added a placeholder clusterversion.TODOPre21_2 alias for 21.2. Replacing those calls with this alias shouldn't change their behavior -- it was already always true, since the code today should never run in a <21.2 cluster -- but means we can delete those older versions in the meantime and then the owners of these bits can decide how to update them.

Partially addresses https://github.com/cockroachdb/cockroach/issues/80663

Release note: None

[cockroach-teamcity]

This change is 

[celiala]

TFTR!

FYI @msirek that I'm removing TestAutoStatsTableSettingsDisallowedOnOldCluster -- please scream and shout if this should be kept!

Removing TestAutoStatsTableSettingsDisallowedOnOldCluster since:

• it was failing (expected "feature not available yet" error but instead got nil)
• it depended on both ClusterLocksVirtualTable and AutoStatsTableSettings -- both of which are 22.1 version gates

[celiala]

TestLogic_external_connection_privileges is failing all of https://github.com/cockroachdb/cockroach/pull/85937 , https://github.com/cockroachdb/cockroach/pull/85938 , https://github.com/cockroachdb/cockroach/pull/85939, so I'm going to assume that it's not related to changes in this commit.

off_test.runfiles/com_github_cockroachdb_cockroach/pkg/sql/logictest/testdata/logic_test/external_connection_privileges:24: SELECT * FROM system.privileges
        expected:
            root      /externalconn/foo  {ALL}         {}
            testuser  /externalconn/foo  {DROP,USAGE}  {}
        but found (query options: "") :
            testuser  /externalconn/foo  {DROP,USAGE}  {}
            root      /externalconn/foo  {ALL}         {}

[celiala]

TFTR!

bors r=msirek

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