Remove most of the old (pre-3.0) pose library:
- Remove The entire `editors/armature/pose_lib.c` file
- Deprecate `Object::poselib` in DNA
- Remove Operators marked as deprecated in T93405
- Remove RNA property `Object.pose_library`
- Add comment to clarify that the call `BLO_read_id_address(reader,
ob->id.lib, &ob->poselib);` handles deprecated data.
Note that this functionality has been documented as deprecated since
Blender 3.2.
What remains of the old pose library: The DNA for action markers
(`bAction::markers`) and the corresponding Python API. This will allow
future versions of Blender to still convert old pose libraries to new
ones (via the Pose Library panel in the Action editor).
Manifest task: T93406
48b5dcdbe8