feat(common): add cmp_by to Sentinelled

[stdrc]

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What's changed and what's your intention?

Add a cmp_by method to Sentinelled and implement Ord with it. This will be used later by RANGE frame support but also nice to have even without RANGE frame support.

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]

Current dependencies on/for this PR:

• main
  • PR feat(common): add cmp_by to Sentinelled #14578 👈
    • PR feat(common): derive Copy for DeltaBTreeMap #14579
      • PR refactor(over window): simplify find_affected_ranges and correct some corner cases #14580
        • PR refactor(over window): generalize WindowBuffer and window function AggregateState #14647
          • PR feat(over window): window function RANGE frame support in frontend #14648
            • PR feat(over window): window function RANGE frame support - backend part #14416

This stack of pull requests is managed by Graphite.