ui,sql: introduce a way to identify query plan distribution shifts

[jasonlmfong]

Add a new timeseries bargraph under the statement page - explain plan tab. This graph is powered by a new protobuff that returns statement execution counts, grouped by plan gists and timestamps.

Partial: #118579
Epic: None
Release Note(ui): introduce a new way to investigate query plan distributions over time.

[cockroach-teamcity]

This change is 

[github-actions]

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[github-actions]

Potential Bug(s) Detected

The three-stage Claude Code analysis has identified potential bug(s) in this PR that may warrant investigation.

Next Steps:
Please review the detailed findings in the workflow run.

Note: When viewing the workflow output, scroll to the bottom to find the Final Analysis Summary.

After you review the findings, please tag the issue as follows:

• If the detected issue is real or was helpful in any way, please tag the issue with O-AI-Review-Real-Issue-Found
• If the detected issue was not helpful in any way, please tag the issue with O-AI-Review-Not-Helpful

[alyshanjahani-crl]

B/c this part of the code and the UI aren't used much I'm fine with this, but before merging try and take a look to see if you can refactor / clean up this
getStatementDetailsPerAggregatedTs + getStatementDetailsPerPlanHash + getStatementDetailsPerAggregateadTsAndPlanHash

Also none of this statement details code has tests, even if you can add a small amount of coverage that would be great.

[jasonlmfong]

TFTR

bors r=alyshanjahani-crl

[craig]

Build succeeded:

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