[SPARK-51203][SQL] Enhance force optimize skewed join

[wForget]

What changes were proposed in this pull request?

Why are the changes needed?

ForceOptimizeSkewedJoin allows optimizing skewed join even if
introduce extra shuffle, but currently it only works for aggregation after join, not for aggregations in children of join. Like:

HashAggregate
     |
  Exchange 
     |
HashAggregate     Exchange (skewed side)
     |               |
   Sort            Sort
     \               /
       SortMergeJoin

I want to introduce extra shuffle for join child so as to optimize skewed join when forceOptimizeSkewedJoin is enabled? Like:

  HashAggregate
       |
    Exchange 
       |
  HashAggregate     
       |
    Exchange
(froce extra shuffle)       Exchange (skewed side)
       |                       |
     Sort                     Sort
       \                      /
      SortMergeJoin(isSkewJoin = true) 

Does this PR introduce any user-facing change?

How was this patch tested?

added unit test

Was this patch authored or co-authored using generative AI tooling?

No