Add two new operators, `anim.slot_new_for_id` and
`anim.slot_unassign_from_id`. These are used in the Action editor and
the Animation panels in the Properties editor, to respectively create a
new Action Slot for an ID and to unassign whatever slot is currently
assigned to that ID.
The latter operator also replaces the C++ operator
`anim.slot_unassign_object`, which was specifically made for the
Dopesheet header. The Python ones are generic enough to be used there
too.
Pull Request: https://projects.blender.org/blender/blender/pulls/126943
a6d7e12e22