973 test abiotic model with different number of canopy layers

[vgro]

This PR updates the tests in the abiotic folder to run with a varying number of canopy layers. This required introducing a few extra functions that deal with NaN and fixing how the layer thickness is calculated. I also fixed a sign error in the temperature updated.

You will see some slightly convoluted masking in some of the tests, that is to check that the true values are not NaN.

I haven't introduced a non-vegetated grid cell, this will be addressed in #975 .

Fixes #973

Type of change

• New feature (non-breaking change which adds functionality)
• Optimization (back-end change that speeds up the code)
• Bug fix (non-breaking change which fixes an issue)

Key checklist

• Make sure you've run the pre-commit checks: $ pre-commit run -a
• All tests pass: $ poetry run pytest

Further checks

• Code is commented, particularly in hard-to-understand areas
• Tests added that prove fix is effective or that feature works
• Relevant documentation reviewed and updated

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.23%. Comparing base (ea7ac16) to head (514b974).
⚠️ Report is 1479 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #976      +/-   ##
===========================================
+ Coverage    94.21%   94.23%   +0.02%     
===========================================
  Files           79       79              
  Lines         6564     6589      +25     
===========================================
+ Hits          6184     6209      +25     
  Misses         380      380              

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[jacobcook1995]

LGTM!