Add back Distinct for where-exists if subquery is a DISTINCT

[ygf11]

Is your feature request related to a problem or challenge? Please describe what you are trying to do.

After #5264, we support rewriting more where-exists to join, but do not add back the Distinct.
For query:

SELECT t1.t1_id
FROM   t1
WHERE  EXISTS(SELECT DISTINCT t2_int
              FROM   t2
              WHERE  t2.t2_id > t1.t1_id); 

# current logical plan:
Projection: t1.t1_id                                                                                                                
  LeftSemi Join:  Filter: t2.t2_id > t1.t1_id                                                                                                               
    TableScan: t1 projection=[t1_id]                                                                                                       
    Projection: t2.t2_id # DISTINCT is not added back                                                                                                                                    
      TableScan: t2 projection=[t2_id]

Although the execution result is correct, we should add back the DISTINCT.
In some cases, DISTINCT can filter a lot rows before join, we should let user choose.

Describe the solution you'd like
Add back Distinct if the subquery is a DISTINCT.

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A clear and concise description of any alternative solutions or features you've considered.

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