So far linked proxies were just kept as-is, this is no longer an option.
Attempt to convert them into liboverrides as much as possible, though
some cases won't be supported:
- Appending proxies is broken since a long time, so conversion will fail
here as well.
- When linking data, some cases will fail to convert properly. in
particular, if the linked proxy object is not instanced in a scene
(e.g. when linking a collection containing a proxy as an
epty-instanced collection instead of a view-layer-instanced collection).
NOTE: converion when linking/appending is done unconditionnaly, option
to not convert on file load will be removed in next commit anyway.
Part of T91671.
049df7ef94