deprecate qt_viewer.screenshot & clipboard

[tlambert03]

Description

Looking into changing the examples for #3066, at least some of the public usage is just to access clipboard and screenshot. Since those methods already exist on viewer.window, which is intended to be our public "gui related" api, this PR deprecates direct usage of viewer.window.qt_viewer.screenshot() in favor of viewer.window.screenshot(canavs_only=True) (matching the canvas_only kwarg already used in Viewer and nbscreenshot)

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

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• example: the test suite for my feature covers cases x, y, and z
• example: all tests pass with my change

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
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[sofroniewn]

Looks great. This now has conflicts (because i got trigger happy on #3066). I'll follow whatever you recommend for fixing @tlambert03 - if you want to revert my merge or if we just press on

[codecov]

Codecov Report

Merging #3765 (8247d2f) into main (d054fdb) will increase coverage by 0.05%.
The diff coverage is 86.39%.

@@            Coverage Diff             @@
##             main    #3765      +/-   ##
==========================================
+ Coverage   83.05%   83.10%   +0.05%     
==========================================
  Files         563      572       +9     
  Lines       46524    46972     +448     
==========================================
+ Hits        38642    39038     +396     
- Misses       7882     7934      +52     

Impacted Files	Coverage Δ
napari/_qt/_tests/test_app.py	60.60% <ø> (-2.26%)	⬇️
napari/_qt/layer_controls/qt_points_controls.py	89.26% <0.00%> (-1.22%)	⬇️
napari/_qt/layer_controls/qt_shapes_controls.py	91.94% <0.00%> (-1.26%)	⬇️
napari/_qt/menus/debug_menu.py	71.42% <0.00%> (ø)
napari/_qt/menus/help_menu.py	100.00% <ø> (ø)
napari/_tests/test_adding_removing.py	100.00% <ø> (ø)
napari/_tests/test_draw.py	36.84% <0.00%> (ø)
napari/_tests/test_examples.py	80.00% <ø> (-0.96%)	⬇️
...ispy/experimental/_tests/test_vispy_tiled_image.py	27.27% <0.00%> (ø)
napari/benchmarks/benchmark_qt_viewer_image.py	0.00% <0.00%> (ø)
... and 124 more

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