Do not broadcast when co-partitioned.

[stuhood]

Which issue does this PR close?

• Closes JoinSelection should check if inputs already satisfy co-partitioning requirements before choosing CollectLeft (broadcast) #25301

Rationale for this change

In JoinSelection, try_collect_left converts a hash join to PartitionMode::CollectLeft (broadcast) when either input is below configured byte/row thresholds. However, if the inputs are already co-partitioned on the join keys across multiple partitions (e.g. both partitioned by hash on the join keys or by range with matching boundaries), switching to CollectLeft introduces an unnecessary CoalescePartitions and broadcasts data across partitions or cluster nodes.

Preserving PartitionMode::Partitioned when the inputs already satisfy the partitioned distribution requirements allows the join to execute locally within each partition with zero shuffles or network transfers.

What changes are included in this PR?

• Added HashJoinExec::partitioned_input_distribution_requirements and HashJoinExec::inputs_satisfy_partitioned_requirements in datafusion/physical-plan/src/joins/hash_join/exec.rs.
• In JoinSelection::try_collect_left (datafusion/physical-optimizer/src/join_selection.rs), skip converting to CollectLeft if inputs already satisfy partitioned distribution requirements across >1 partition.

What is the testing strategy for this PR?

New unit tests.

Are there any user-facing changes?

No.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 91.13924% with 7 lines in your changes missing coverage. Please review.
✅ Project coverage is 81.91%. Comparing base (6bbd3f4) to head (4735398).
⚠️ Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
...tafusion/physical-plan/src/joins/hash_join/exec.rs	92.10%	0 Missing and 6 partials ⚠️
...atafusion/physical-optimizer/src/join_selection.rs	66.66%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #25304      +/-   ##
==========================================
- Coverage   81.91%   81.91%   -0.01%     
==========================================
  Files        1134     1134              
  Lines      425708   425722      +14     
  Branches   425708   425722      +14     
==========================================
+ Hits       348726   348729       +3     
  Misses      56305    56305              
- Partials    20677    20688      +11     

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