Fixes handling multiple z axes when vertically regridding

[jasonb5]

Description

• Closes [Bug]: ds.regridder.vertical() breaks with KeyError: 0 if grid_positions=None and input_grid has multiple Z axis  #519
  • Fixes correctly dropping extra Z coordinates when using the accessory method.
  • Raises exception if multiple Z coordinates are present in input grid.
• Closes [DevOps]: Fix build job not properly updating mamba env if cache not found, causing pytest to not be found in env #530

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• My changes generate no new warnings
• Any dependent changes have been merged and published in downstream modules

If applicable:

• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass with my changes (locally and CI/CD build)
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have noted that this is a breaking change for a major release (fix or feature that would cause existing functionality to not work as expected)

[tomvothecoder]

Hey @jasonb5, here is my code review. I pushed a commit instead of suggesting changes because it was easier to do. Let me know if you agree with my changes.

I'll try to fix the build workflow and merge once the PR is ready.

[jasonb5]

@tomvothecoder I'm fine with these changes, thanks.

[codecov]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (870b334) 100.00% compared to head (c6e9d20) 100.00%.

❗ Current head c6e9d20 differs from pull request most recent head 52129c9. Consider uploading reports for the commit 52129c9 to get more accurate results

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #525   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           15        15           
  Lines         1562      1590   +28     
=========================================
+ Hits          1562      1590   +28     

Files Changed	Coverage Δ
xcdat/regridder/accessor.py	100.00% <100.00%> (ø)
xcdat/regridder/base.py	100.00% <100.00%> (ø)
xcdat/regridder/xgcm.py	100.00% <100.00%> (ø)

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[tomvothecoder]

Thanks @jasonb5. I'm fixing up the build workflow and will merge this PR once I'm done.