release-24.1: sqlstats: generate PCT_RUNTIME sort when requested

[blathers-crl]

Backport 1/1 commits from #123846 on behalf of @dhartunian.

/cc @cockroachdb/release

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Previously, when a request was made to the combined stats endpoint on CRDB with a PCT_RUNTIME sort, we'd default to a svcLatency sort instead because of a missing switch case.

This change fills that gap and adds some datadriven tests to inspect the resulting WHERE clauses.

Fixes: #123841
Epic: CRDB-37544

Release note (ui change): Viewing SQL Activity sorted by % of Runtime now correctly sorts entries by the runtime amount.

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Release justification: low-risk, high-impact bugfix for sql stats

[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.
• Backports should not break backwards-compatibility.
• Backports should change as little code as possible.
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• Backports should not add new functionality (except as defined
  here).
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If your backport adds new functionality, please ensure that the following additional criteria are satisfied:

• 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. State changes must be further protected such that nodes running old binaries will not be negatively impacted by the new state (with a mixed version test added).
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Also, please add a brief release justification to the body of your PR to justify this
backport.

[cockroach-teamcity]

This change is