Improvements to GUI selection and Qt support

[almarklein]

Closes #384

• Adds a new fpl.utils/gui module where the GUI selection is handled and nothing else.
• Fastplotlib lists its own GUI preference order, but respects users who override it.
• Avoid importing multiple GUI libraries.
  • This makes fpl lighter.
  • In my experience importing multiple GUI frameworks can also result in odd bugs.
  • Remove all imports of wgpu.gui.auto except in fpl.utils.gui.
  • Users can still use a custom canvas and thus mix GUI toolkits if they want to go crazy :)
• The fpl.run() method now matches the GUI backend in use (this was not necessarily the case previously).
• Support for all modern Qt libraries!
• The cases where ipywidgets is imported is now conditional (only happens in Jupyter notebook / lab).

Note on performance: The import time is about 0.2 s faster on desktop (because it does not import Jupyter stuff). In the notebook we can expect a similar improvement because glfw and qt are not imported by default (when available).

[almarklein]

Ready for review, but I figure you may want to have a code-review before letting CI run 😄

[almarklein]

Funny how pygfx/pygfx#674 gets reported while we're working on this 😄 I think I'll put this PR on hold, and first address the GUI backend selection mechanics. I think your code to check what GUI Jupyter has integrated should be used in wgpu-py. And perhaps it makes sense to provide more ways to influence backend preference, that fpl can then use (in the new gui.py).

[kushalkolar]

yup makes sense to do it upstream, less wheel reinventing 😄

[kushalkolar]

After pygfx/wgpu-py#478 it should be possible to greatly simplify this

[almarklein]

I made some updates to make it work with the latest wgpu. Ready from my end!

[kushalkolar]

This is really great, thanks! 🥳 . Will merge once wgpu v0.15.1 is on pypi and tests pass