release-22.2: upgrades: repair broken 22.1 migration so 22.2 migration works

[ajwerner]

Backport 1/1 commits from #91304.

/cc @cockroachdb/release

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This also fixes the logic which allowed the 22.1 migration to proceed in the
first place. This will need to be backported to 22.2. Any users which upgraded
from 21.2->22.1->22.2.did_not_contain_this_patch will not have the correct
indexes on their system.statement_diagnostics_requests table.

Fixes #91300

Release justification: Fixes a feature-impacting migration.

Release note (bug fix): Fixed a bug which caused a migration in 22.1 to fail
to drop an index on system.statement_diagnostics_requests and, in turn, caused
upgrades from 22.1->22.2 which had used the previous, faulty upgrade migration
to now fail to create a new index with the same name as the index which had
been thought to have been dropped.

[blathers-crl]

Thanks for opening a backport.

Please check the backport criteria before merging:

• Patches should only be created for serious issues or test-only changes.
• Patches should not break backwards-compatibility.
• Patches should change as little code as possible.
• Patches should not change on-disk formats or node communication protocols.
• Patches should not add new functionality.
• Patches must not add, edit, or otherwise modify cluster versions; or add version gates.

If some of the basic criteria cannot be satisfied, ensure that the exceptional criteria are satisfied within.

• There is a high priority need for the functionality that cannot wait until the next release and is difficult to address in another way.
• The new functionality is additive-only and only runs for clusters which have specifically “opted in” to it (e.g. by a cluster setting).
• New code is protected by a conditional check that is trivial to verify and ensures that it only runs for opt-in clusters.
• The PM and TL on the team that owns the changed code have signed off that the change obeys the above rules.

Add a brief release justification to the body of your PR to justify this backport.

Some other things to consider:

• What did we do to ensure that a user that doesn’t know & care about this backport, has no idea that it happened?
• Will this work in a cluster of mixed patch versions? Did we test that?
• If a user upgrades a patch version, uses this feature, and then downgrades, what happens?

[cockroach-teamcity]

This change is 

[maryliag]

Reviewable status: complete! 1 of 0 LGTMs obtained

[ajwerner]

TFTR!