feat(over window): add compute count metric for general over window executor

[stdrc]

I hereby agree to the terms of the RisingWave Labs, Inc. Contributor License Agreement.

What's changed and what's your intention?

Add a metric displaying compute count and same result count for general over window executor, which can serve as a guide for further optimization to result re-computation.

Checklist

• I have written necessary rustdoc comments
• I have added necessary unit tests and integration tests
• I have added test labels as necessary. See details.
• I have added fuzzing tests or opened an issue to track them. (Optional, recommended for new SQL features Sqlsmith: Sql feature generation #7934).
• My PR contains breaking changes. (If it deprecates some features, please create a tracking issue to remove them in the future).
• All checks passed in ./risedev check (or alias, ./risedev c)
• My PR changes performance-critical code. (Please run macro/micro-benchmarks and show the results.)

• My PR contains critical fixes that are necessary to be merged into the latest release. (Please check out the details)

Documentation

• My PR needs documentation updates. (Please use the Release note section below to summarize the impact on users)

Release note

If this PR includes changes that directly affect users or other significant modifications relevant to the community, kindly draft a release note to provide a concise summary of these changes. Please prioritize highlighting the impact these changes will have on users.

[stdrc]

• feat(over window): add compute count metric for general over window executor #18847 👈
• refactor(over window): move build_changes to OverPartition for better modularity #18846
• main

This stack of pull requests is managed by Graphite. Learn more about stacking.

Join @stdrc and the rest of your teammates on Graphite

[Li0k]

LGTM, thanks for the effort