Add skewness metric to nodes that execute in partitioned mode

[LiaCastaneda]

Which issue does this PR close?

Related to #23237 and feat(metric): Add output skewness metric to detect skewed plans easier

• Closes #.

Rationale for this change

I think it would be useful to add the skewness metric for nodes that execute in partitioned mdoe -- right now the only node that includes that metric in the explain analyze is DataSourceExec for parquet.

This is specially useful to check how many partitions were idle during Aggregations or HashJoins for example.

What changes are included in this PR?

The PR adds a new metric output_rows_skew in the Explain Analyze output for the following nodes:

• RepartitionExec
• HashJoinExec
• AggregateExec
• BoundedWindowAggExec
• WindowAggExec

Note that for a plan that has a Parquet DataSource the skewness might not be the same as for the rest of the nodes, for example we might have the following scenario:

DataSourceExec       [100, 100, 100, 100]  → 0% skewness, data is even
  FilterExec         [100,   0,   0,   0]  → 100%   (filter only matches in partition 0)
    AggregateExec    [  3,   0,   0,   0]  → 100%   (Partial: groups, not rows)
      RepartitionExec Hash  [1, 1, 1, 0]   → ~11%   (3 groups re-spread by key)

What is the testing strategy for this PR?

I added a Explain Analyze test

Are there any user-facing changes?

Yes, a new metric will show in the explain analyze plan for the nodes mentioned above.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 90.90909% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 82.61%. Comparing base (c922f88) to head (ed306cb).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
...usion/physical-plan/src/windows/window_agg_exec.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #25977      +/-   ##
==========================================
- Coverage   82.61%   82.61%   -0.01%     
==========================================
  Files        1147     1147              
  Lines      444812   444818       +6     
  Branches   444812   444818       +6     
==========================================
- Hits       367502   367494       -8     
- Misses      54996    55006      +10     
- Partials    22314    22318       +4     

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[rgbuilds]

The new metric accounting looks sound, and the focused EXPLAIN ANALYZE test and affected SQL logic tests pass locally.

One small documentation suggestion: explain-usage.md currently lists output_rows_skew under Parquet scans; could it also mention the operators added here?

[gabotechs]

👍 Nice! no comments, looks good to me

[LiaCastaneda]

Thanks for the reviews!

One small documentation suggestion: explain-usage.md currently lists output_rows_skew under Parquet scans; could it also mention the operators added here?

I will make a small PR shortly :)

[LiaCastaneda]

micro PR: #26048