perf: skip evaluating fully calculated window partitions

[neilconway]

Which issue does this PR close?

• Related to BoundedWindowAggExec in Linear mode is slow for many-partitions #23982

Rationale for this change

In Linear mode, BoundedWindowAggStream's evaluation sweep visits every live partition for every window expression on every input batch. A partition can be safely skipped if it received no new rows and already row currently in the partition has its output fully computed. This avoids a bunch of redundant work: re-evaluating the window function arguments and ORDER BY columns against the retained batch, building an empty result array, and other bookkeeping. This is particularly expensive for workloads with many partitions where only a few of those partitions receive rows in a given batch, as in the "32k sparse" benchmark below.

Benchmarks:

• linear / range / single / 100 dense: 42.3 ms -> 42.0 ms (~noise)
• linear / range / single / 10000 dense: 158.7 ms -> 152.5 ms (-3.9%)
• linear / range / single / 32768 sparse: 161.1 ms -> 108.0 ms (-33.0%)
• linear / rows / single / 10000 dense: 132.0 ms -> 127.5 ms (-3.4%)
• linear / range / multi / 10000 dense: 255.9 ms -> 236.4 ms (-7.6%)
• sorted / range / single / 10000: 33.1 ms -> 33.7 ms (~noise)

What changes are included in this PR?

• Skip evaluating window expressions for fully calculated partitions
• Add test case
• Add assert checking that per-window-agg and per-partition state is consistent

Are these changes tested?

Yes. Existing tests pass. Added a new test to verify that "evaluate partition -> skip partition -> evaluate partition" sequence results in resuming accumulator states appropriately. I also checked that if the is_end conjunct is removed from the skip condition, the new assert added above fires and catches the bug.

Are there any user-facing changes?

No.

[neilconway]

cc @Dandandan ; similar in spirit to other recent optimization PRs to skip per-partition work when it is a no-op

[codecov-commenter]

Codecov Report

❌ Patch coverage is 85.10638% with 14 lines in your changes missing coverage. Please review.
✅ Project coverage is 81.02%. Comparing base (3e3a92d) to head (3cbaae8).
⚠️ Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
...ysical-plan/src/windows/bounded_window_agg_exec.rs	82.27%	3 Missing and 11 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #24127      +/-   ##
==========================================
+ Coverage   80.91%   81.02%   +0.10%     
==========================================
  Files        1103     1105       +2     
  Lines      377219   379798    +2579     
  Branches   377219   379798    +2579     
==========================================
+ Hits       305244   307743    +2499     
- Misses      53775    53823      +48     
- Partials    18200    18232      +32     

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.