minor(test): cover partially ordered aggregate spilling

[buraksenn]

Which issue does this PR close?

• Not closes but part of Improve test coverage for spilling (memory-limited) sort/aggregation/sort-merge-join #13431

Rationale for this change

GroupedHashAggregateStream supports spilling for partially sorted group input, but existing aggregate spill tests only cover unordered (GroupOrdering::None) input. The GroupOrdering::Partial + OutOfMemoryMode::Spill path, including spilling sorted intermediate state and merging it back, does not have direct coverage.

What changes are included in this PR?

added test coverage for the case above

Are these changes tested?

test only change and it can be tested via:

    cargo test -p datafusion-physical-plan partially_sorted_single_aggregate_spills_and_matches

Are there any user-facing changes?

no test only change

[codecov-commenter]

Codecov Report

❌ Patch coverage is 74.64789% with 18 lines in your changes missing coverage. Please review.
✅ Project coverage is 80.69%. Comparing base (994fc81) to head (d7a29d9).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
datafusion/physical-plan/src/aggregates/mod.rs	74.64%	3 Missing and 15 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #23947      +/-   ##
==========================================
- Coverage   80.69%   80.69%   -0.01%     
==========================================
  Files        1095     1095              
  Lines      372626   372697      +71     
  Branches   372626   372697      +71     
==========================================
+ Hits       300700   300735      +35     
- Misses      53978    53993      +15     
- Partials    17948    17969      +21     

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[2010YOUY01]

LGTM, thank you!

This suggestion is totally optional, it would be great to move it to sqllogictest, due to 1. the test can be stronger as it exercises the behavior end-to-end 2. easier to maintain (I found rust tests regularly need updates during refactors, and they're harder to review)

To do that, sqllogictest provides Rust hooks to setup tables with orders, and we can use explain/explain analyzes to assert if the ordered path is triggered, and if spill happens.