Renaming of proxy vars for contours and overlays

[lewisblake]

Change Summary

Grabs the renaming of variables from a config for contours and overlays if provided. Otherwise, the original variable name is used.

Related issue number

Close #902

Checklist

• Start with a draft-PR
• The PR title is a good summary of the changes
• PR is set to AeroTools and a tentative milestone
• Documentation reflects the changes where applicable
• Tests for the changes exist where applicable
• Tests pass locally
• Tests pass on CI
• At least 1 reviewer is selected
• Make PR ready to review

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 78.46%. Comparing base (ee2f859) to head (9591a7d).
Report is 10 commits behind head on main-dev.

Additional details and impacted files

@@             Coverage Diff              @@
##           main-dev    #1489      +/-   ##
============================================
- Coverage     78.46%   78.46%   -0.01%     
============================================
  Files           139      139              
  Lines         21120    21119       -1     
============================================
- Hits          16571    16570       -1     
  Misses         4549     4549              

Flag	Coverage Δ
unittests	78.46% <ø> (-0.01%)	⬇️

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