Fix aliasing in queries by keeping required projections

[GuptaManan100]

Description

This PR fixes the issue pointed out in #15944.

The problem was that we were removing some Projection operators that were only passing through the columns in the same order that they were receiving in. However, they were changing the column aliases. These projections are still required and should not be removed.

Related Issue(s)

• Fixes Bug Report: Incorrect column name in a derived query #15944

Checklist

• "Backport to:" labels have been added if this change should be back-ported to release branches
• If this change is to be back-ported to previous releases, a justification is included in the PR description
• Tests were added or are not required
• Did the new or modified tests pass consistently locally and on CI?
• Documentation was added or is not required

Deployment Notes

[vitess-bot]

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 68.43%. Comparing base (8639de2) to head (d9190c3).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #15943      +/-   ##
==========================================
+ Coverage   68.41%   68.43%   +0.02%     
==========================================
  Files        1562     1562              
  Lines      197056   197052       -4     
==========================================
+ Hits       134807   134850      +43     
+ Misses      62249    62202      -47     

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[deepthi]

Is this a bug that only exists on main aka v20? Are any back ports needed?

[GrahamCampbell]

I have replicated this bug on V19.

[systay]

We need to backport this all the way to V17

[GuptaManan100]

I checked at it doesn't help to back port this change to any of the releases. It is actually correct in the other releases. We introduced the capability to change the column names in simple projection in #15384, before that removing the simple projection if it was only passing through the columns was actually correct.
Even if we back port this change, the query doesn't work. I'm closing all the other PRs.