chore(pgwire): add start of execution logs for all queries

[kwannoel]

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What's changed and what's your intention?

If PGWIRE_QUERY_LOG is enabled, we will also log at the start of query execution, not just when the query finishes execution. This allows us to review queries which encounter OOM or abort which can't be caught by the runtime. The result is that we will lose these queries that were executed.

A note on overhead: Currently, if PGWIRE_QUERY_LOG=info is set, we will already emit at least one log for the query on its completion. We add one more log line for start of execution. If the overhead is too high for the user, they can always switch off query logging.

If the overhead is unacceptable, we could downgrade the log level to debug. But I prefer to keep it enabled, or else we have to wait for the event to occur.

Checklist

• I have written necessary rustdoc comments.
• I have added necessary unit tests and integration tests.
• I have added test labels as necessary.
• I have added fuzzing tests or opened an issue to track them.
• My PR contains breaking changes.
• My PR changes performance-critical code, so I will run (micro) benchmarks and present the results.
• I have checked the Release Timeline and Currently Supported Versions to determine which release branches I need to cherry-pick this PR into.

Documentation

• My PR needs documentation updates.

Release note

[kwannoel]

Currently only extended query mode will log their parsing step. We miss some local query executions, which might still be heavy.

[github-actions]

✅ Cherry-pick PRs (or issues if encountered conflicts) have been created successfully to all target branches.

[github-actions]

✅ Cherry-pick PRs (or issues if encountered conflicts) have been created successfully to all target branches.