Cleanup and enhance our export of the USD `extent` attribute.
This does the following:
- The existing `author_extents` function now uses recently added common
code to write out the extents attribute
- A new `author_extents` overload allows the use of Blender's native
bounds for the types that support it. We now use this rather than
asking USD to recompute it for us.
- Meshes will now have their extents correctly written during animations
- Curves will now have their extents written as they were not doing so
prior to this PR
- Hair, Lights, Points, and Volumes make use of the `author_extents`
functions now
Since Curves need their extents tested, this PR also moves the test from
C++ to Python. Python tests allow for faster iteration, are more
straightforward to write, and allow usage of the USD validator.
Pull Request: https://projects.blender.org/blender/blender/pulls/132531
1ceaaeeff7