Update `BKE_fcurves_id_cb(id, callback)` so that it only reports
F-Curves for `id`. With legacy Actions this used to be "all F-Curves in
the Action", but with slotted Actions it should only report the F-Curves
for the assigned slot.
`BKE_fcurves_id_cb()` is used in two places:
1. Updating F-Curve paths in versioning, for example when node sockets
were added/removed. For this it is vital that the updates only happen
for those nodes that were actually affected by this versioning code,
and not blindly for all F-Curves in the Action.
2. Marking properties as 'animated' in the depsgraph, and the 'value
backup' for those properties. This should also be only done for the
properties of that ID, and thus be limited to the F-Curves for the
assigned slot.
Pull Request: https://projects.blender.org/blender/blender/pulls/134851
3fd430d1c6