[WIP] support PartialMerge

[comphead]

Which issue does this PR close?

Closes #2870 .

Rationale for this change

What changes are included in this PR?

How are these changes tested?

[comphead]

Investigating what would be broken for supporting PartialMerge

[comphead]

so Spark creates intermittent columns which in scope only for partialmerge and then dropped, however it leads to

        internal_err!("UnboundColumn::evaluate() should not be called")

We probably need to mock those columns

[codecov-commenter]

Codecov Report

❌ Patch coverage is 78.26087% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 54.67%. Comparing base (f09f8af) to head (4353f3a).
⚠️ Report is 811 commits behind head on main.

Files with missing lines	Patch %	Lines
...n/scala/org/apache/spark/sql/comet/operators.scala	78.26%	1 Missing and 4 partials ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #2918      +/-   ##
============================================
- Coverage     56.12%   54.67%   -1.46%     
- Complexity      976     1257     +281     
============================================
  Files           119      167      +48     
  Lines         11743    15500    +3757     
  Branches       2251     2570     +319     
============================================
+ Hits           6591     8474    +1883     
- Misses         4012     5810    +1798     
- Partials       1140     1216      +76     

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