release-23.2: sql: fix query start time for begin statements

[blathers-crl]

Backport 1/1 commits from #114831 on behalf of @xinhaoz.

/cc @cockroachdb/release

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Previously, the query age for BEGIN statements appearing in logs (sql-exec, sql-audit, telemetry) was being incorrectly recorded. This is because the start time being passed was from the stats collector, which was not up to date with the session phase times at the time of executing BEGIN. This patch fixes the query age for BEGIN stmt logs by using the session phase times directly from the conn executor for BEGIN stmt logging instead reading them from the stats collector.

Epic: none
Fixes: #114571

Release note (bug fix): BEGIN statement logs now have correct query Age fields. Previously, these fields were being recorded incorrectly which would lead to some statements also appearing erroneously in the slow query logs.

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Release justification: bug fix GA blocker

[blathers-crl]

Thanks for opening a backport.

Please check the backport criteria before merging:

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  issues or test-only changes.
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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 

[dhartunian]

Reviewable status: complete! 1 of 0 LGTMs obtained (waiting on @abarganier and @xinhaoz)