The `animrig::assign_action(action, id)` function now takes a `bAction`
pointer (instead of its C++ wrapper `animrig::Action`). This makes it
easier to call from code that just deals with the DNA/C struct.
Also an override was added that takes an `OwnedAnimData` struct instead
of just the ID. This saves the lookup of the AnimData, to be used in cases
where the caller already has it.
Pull Request: https://projects.blender.org/blender/blender/pulls/128030
99d4c3c44d