refactor!: drop redundant alias fields

[stuarttimwhite]

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Rationale for this change

The aliases for count on aggregation and the results for sort merge join are already available in the output_column_names field when running try_into_proof_plan, and they are not used for verification, so it is safe to remove them from the EVM plans.

What changes are included in this PR?

Removing count alias and result aliases from group by/aggregate and sort merge join, respectively.

Are these changes tested?

Yes

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.70%. Comparing base (b0ea8a6) to head (df8c2c0).
⚠️ Report is 59 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1073      +/-   ##
==========================================
+ Coverage   96.66%   96.70%   +0.03%     
==========================================
  Files         299      299              
  Lines       58060    58446     +386     
==========================================
+ Hits        56124    56518     +394     
+ Misses       1936     1928       -8     

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[github-actions]

This PR has been marked as stale due to 30 days of inactivity. It will be closed in 7 days if no further activity occurs.