ci: Update CI workflow to include reusable test

[tlambert03]

updates tests to use:

• https://github.com/pyapp-kit/workflows/blob/main/.github/workflows/test-pyrepo.yml for running tests
• https://github.com/pyapp-kit/workflows/blob/main/.github/workflows/test-dependents.yml - for testing things that depend on app-model, like napari

closes #129

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (668544b) 100.00% compared to head (ad577b4) 100.00%.

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #150   +/-   ##
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  Coverage   100.00%   100.00%           
=========================================
  Files           31        31           
  Lines         1783      1783           
=========================================
  Hits          1783      1783           

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