Split out builtins into another top-level module

[tlambert03]

Description

This PR would split our "builtins" plugins into a new top-level module napari_builtins. In this PR, it remains distributed with napari package on PyPI. If we want to go in this direction (as has been discussed) i think it would be good to have at least a little period of co-existence of the two packages in the same repo, since I think there will likely be some follow-ups. Particularly with regards to testing: we currently do a lot of sorta-kinda indirect integration testing and it would be a good opportunity to clean up our tests to clarify whether we're testing how napari calls plugins, vs how our builtin plugin works.

i think most tests are passing currently, but still in draft cause I want to go back and clean up the tests even more

Type of change

• Bug-fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

References

How has this been tested?

• example: the test suite for my feature covers cases x, y, and z
• example: all tests pass with my change
• example: I check if my changes works with both PySide and PyQt backends
  as there are small differences between the two Qt bindings.

Final checklist:

• My PR is the minimum possible work for the desired functionality
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• If I included new strings, I have used trans. to make them localizable.
  For more information see our translations guide.

[Czaki]

when we move part of code to new top level package, then maybe new entry should be added to coverage.status.project in coverage.yaml?

[codecov]

Codecov Report

Merging #4706 (a63c58f) into main (e1f6779) will decrease coverage by 0.08%.
The diff coverage is 91.66%.

@@            Coverage Diff             @@
##             main    #4706      +/-   ##
==========================================
- Coverage   87.68%   87.59%   -0.09%     
==========================================
  Files         589      580       -9     
  Lines       50631    49715     -916     
==========================================
- Hits        44394    43549     -845     
+ Misses       6237     6166      -71     

Impacted Files	Coverage Δ
napari/plugins/__init__.py	84.84% <0.00%> (+2.49%)	⬆️
napari/utils/io.py	78.94% <ø> (-10.58%)	⬇️
napari/_qt/_tests/test_qt_viewer.py	94.26% <100.00%> (ø)
napari/_qt/qt_viewer.py	71.39% <100.00%> (+0.63%)	⬆️
napari/components/_tests/test_viewer_labels_io.py	100.00% <100.00%> (ø)
napari/conftest.py	92.97% <100.00%> (+2.44%)	⬆️
napari/types.py	89.47% <0.00%> (-7.50%)	⬇️
napari/components/experimental/chunk/_pool.py	85.71% <0.00%> (-3.18%)	⬇️
napari/plugins/io.py	50.00% <0.00%> (-2.55%)	⬇️
napari/components/experimental/chunk/_loader.py	71.66% <0.00%> (-1.67%)	⬇️
... and 14 more

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[brisvag]

Seems like a real fail... are the readers actually being installed?

[tlambert03]

Yeah agreed, will look. They certainly make it into the local sdist/wheel.

[sofroniewn]

Love this so much! @tlambert03 if you can chase down that test fail then I think this can merge!! 🚀

[tlambert03]

that seems to have fixed it, just split up the --pyargs tests into two steps

[sofroniewn]

Nice - all tests now passing. Let's see if @jni has any comments on this - otherwise i think it's good to merge!

[sofroniewn]

This has been approved for a week now - unless hearing anything else by tomorrow I will merge, thanks all!!!