release-24.1: sql: fix TestValidationWithProtectedTS flake

[blathers-crl]

Backport 1/1 commits from #123750 on behalf of @fqazi.

/cc @cockroachdb/release

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Previously, the test TestValidationWithProtectedTS would hang if a Ggio routine would hit an error, since a channel would not be posted on a error. It would also not gracefully handle TS after replica GC errors on transactions, which could happen on overloaded machines. To address this patch makes the test more resilient to the Go routine hitting errors so that it doesn't time out, and adds retry logic for TS after replica GC errors.

Fixes: #123447
Release note: None

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Release justification: test only change

[blathers-crl]

Thanks for opening a backport.

Please check the backport criteria before merging:

• Backports should only be created for serious
  issues or test-only changes.
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[cockroach-teamcity]

This change is