fix: evaluate window aggregate arguments after FILTER

[lyne7-sc]

Which issue does this PR close?

• Closes Window aggregate FILTER evaluates arguments for rejected rows #24507.

Rationale for this change

Window aggregates evaluate their arguments before applying FILTER, which can cause errors on rows that should not participate in the aggregate.

This is analogous to #24444 for grouped aggregates, window aggregates use a separate evaluation path.

What changes are included in this PR?

Evaluate the window aggregate filter before evaluating its arguments.

Use the resulting filter mask as a selection when evaluating argument expressions. Selected results are scattered back to the original batch length so that window frame row indices remain aligned.

This applies to both ever-expanding and sliding aggregate window frames.

Are these changes tested?

Yes.

Are there any user-facing changes?

Window aggregate arguments are no longer evaluated for rows rejected by FILTER, no public API changes.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 70.00000% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 81.27%. Comparing base (bb038a6) to head (f2929bc).
⚠️ Report is 38 commits behind head on main.

Files with missing lines	Patch %	Lines
datafusion/physical-expr/src/window/window_expr.rs	70.00%	0 Missing and 3 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #24508      +/-   ##
==========================================
+ Coverage   81.23%   81.27%   +0.03%     
==========================================
  Files        1112     1116       +4     
  Lines      390635   395026    +4391     
  Branches   390635   395026    +4391     
==========================================
+ Hits       317350   321063    +3713     
- Misses      54650    55166     +516     
- Partials    18635    18797     +162     

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[neilconway]

This approach makes sense and is simple and clean, but I'd be curious to understand how it influences performance, especially for simple and infallible expressions (e.g., bare column references).