Ensure consistent order of pose bones. Now it should always match the
one from bones in armature obdata (as exposed by e.g. RNA, i.e.
children-first).
Previously when some pose bones would need to be added or removed from a
pose due to changes in the bone armature, or if bones in armature were
re-ordered, the bones order in pose would not match anymore the one from
armature, and could even become different between e.g. a proxy and its
linked source.
This was not really nice, but not a big issue before either. But with
diffing process of override, consistent order of items between reference
linked collection and local override one is crucial.
Reviewed By: #animation_rigging, sybren
Maniphest Tasks: T82758
Differential Revision: https://developer.blender.org/D9646
fbdf1af355