[I] Avoid using Projections in generic Merge Into DMLs [hudi]

["hudi-bot (via GitHub)" <gi...@apache.org>]

hudi-bot opened a new issue, #15635:
URL: https://github.com/apache/hudi/issues/15635

   Currently, `MergeIntoHoodieTableCommand` squarely relies on semantic implemented by `ExpressionPayload` to be able to insert/update records.
   
   While this is necessary since MIT semantic enables users to do sophisticated and fine-grained updates (for ex, partial updating), this is not necessary in the most generic case:
   
    
   {code:java}
   MERGE INTO target
   USING ... source
   ON target.id = source.id
   WHEN MATCHED THEN UPDATE *
   WHEN NOT MATCHED THEN INSERT *{code}
   This is essentially just a SQL way of implementing an upsert – if there are matching records in the table we update them, otherwise – insert.
   
   In this case there's actually no need to use ExpressionPayload at all, and we can just simply use normal Hudi upserting flow to handle it (avoiding all of the ExpressionPayload overhead)
   
   ## JIRA info
   
   - Link: https://issues.apache.org/jira/browse/HUDI-5405
   - Type: Bug
   - Epic: https://issues.apache.org/jira/browse/HUDI-3249
   - Affects version(s):
     - 0.12.1
   - Fix version(s):
     - 1.1.0


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