Add projection support to SortMergeJoinExec #24518

Is your feature request related to a problem or challenge?

SortMergeJoinExec emits every column of both inputs.
We can add projection support to only produce the output columns (saving some compute / copy).

select * from t1 right join t2 on t1.c3 = t2.c3   -- c3 needs a cast

ProjectionExec: expr=[c1@0 as c1, ..., c4@8 as c4]
  SortMergeJoinExec: join_type=Right, on=[(CAST(t1.c3 AS Decimal128(10, 2))@4, c3@2)]

The cast column is only there to be joined on, and every operator above the join
carries it until the projection removes it.

Describe the solution you'd like

Add projection support to SortMergeJoinExec

Describe alternatives you've considered

No response

Additional context

No response