Re-adopt pydot

[chrizzFTD]

Needs networkx/networkx#7606 to be released.

Thanks to networkx/networkx#7204 pydot is supported again by networkx.

If locked in python-3.9, the last supported combo with this update is:

• networkx==2.8.3 (or older)
• pydot-3.0.1 (or newer)

Additions

• Attribute context menu items in USDView for clearing and blocking values
• Extend CI to test USD-21.11 + Python-3.9
• Support Maya-2025 (which uses PySide6)
• Test data for faster tests

Changes

• Drop pygraphviz instead of pydot. With this update, install issues like pip install errors out on graphviz #37 are gone.
• Removed sphinx_autodoc_typehints since it led to singledispatched / overloaded functions to not appear in sphinx docs (would need to track down why / where, but seems close to Doesn't interact correctly with typing.overload. tox-dev/sphinx-autodoc-typehints#296)

[codecov]

Codecov Report

Attention: Patch coverage is 98.63388% with 5 lines in your changes missing coverage. Please review.

Project coverage is 92.73%. Comparing base (2c09127) to head (b7c3fa0).

Files with missing lines	Patch %	Lines
grill/views/_graph.py	95.23%	3 Missing ⚠️
grill/views/_qt.py	60.00%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop      #40      +/-   ##
===========================================
- Coverage    92.83%   92.73%   -0.11%     
===========================================
  Files           17       17              
  Lines         3826     3718     -108     
===========================================
- Hits          3552     3448     -104     
+ Misses         274      270       -4     

Files with missing lines	Coverage Δ
grill/cook/__init__.py	100.00% <100.00%> (+0.35%)	⬆️
grill/usd/__init__.py	100.00% <100.00%> (ø)
grill/views/_core.py	91.88% <ø> (-0.15%)	⬇️
grill/views/description.py	92.55% <100.00%> (-0.55%)	⬇️
tests/test_cook.py	100.00% <100.00%> (ø)
tests/test_usd.py	100.00% <ø> (ø)
tests/test_views.py	100.00% <100.00%> (ø)
grill/views/_qt.py	73.68% <60.00%> (-6.32%)	⬇️
grill/views/_graph.py	78.26% <95.23%> (+1.47%)	⬆️

... and 1 file with indirect coverage changes