Either initial fix (9405bd25d6) was not fully correct (and properly
tested), or something else changed since then, but the handling of
liboverrides in copy/paste of poses would not be correct for local
overrides.
Instead of relying on generic `BKE_lib_id_make_local` to also work
for local liboverrides, add some more logic in `PartialWriteContext::make_local`
to properly handle local liboverrides when the override data needs to get
removed in the copy buffer blendfile.
NOTE: Not super-happy with how make local and removal of liboverrides
somewhat mix together currently. Will need to revisit once again that
whole process at some point.
0e0b7e3294