The mesh velocity data was not using the UsdUtilsSparseValueWriter and
was writing out data for all frames even if the velocity didn't change.
Adds test coverage for this scenario as well as other situations where a
MeshSequenceCache (MSC) would be required:
- Ensures that when positions vary a MSC is added
- Ensures that when velocities vary a MSC is added (see blender/blender@c862d40e09)
- Ensures that when attributes vary a MSC is added (see blender/blender@3c394d39f2)
Pull Request: https://projects.blender.org/blender/blender/pulls/126208
56779c7bb0