This patch makes it so collection assignments of bones are
symmetrized when the "Symmetrize" operator is run.
* Only collections with names that can be symmetrized are modified.
* Collections are created if they don't exist,
they are created under the same parent as the source collection
* In the case of a "left" bone assigned to a "right" collection the
resulting "right" bone will be assigned to a "left" collection.
The system does explicitly not try to be smart here.
Also adds unit tests.
Pull Request: https://projects.blender.org/blender/blender/pulls/130524
16c2e71ab0