CreateAsset, as it turns out, can be extremely slow, particularly when used on Mesh objects.
By adding our generated objects as sub-objects of a container AnimatorController, we can
minimize this overhead.
This branch rewrites the merge armature logic to be both simpler and more reliable. In particular, all components in the merged armature will always be moved into the target armature, eliminating the need for complex and unreliable constraint adjustments. I also rewrite the path remapping logic to be more reliable by tracking actual GameObjects, rather than string paths.
This change fixes a number of constraint-heavy outfits, including:
* https://cloudz.booth.pm/items/3751948
* https://capettiya.booth.pm/items/4424678
It also fixes issues with some more advanced use cases, such as animating transforms on bones that are newly added using merge armature.
