After remapping there is no guarantee that collections' parent pointers
are still valid, so using these to free the object cache of all the
collections' ancestors is potentially accessing invalid memory.
Further more, it is noticiably inefficient, as a same collection may be
processed many times.
So instead, introduce (and use in resync case) a new
`BKE_main_collections_object_cache_free`, which iterates over all
collections of given Main and only free their own cache.
Implement ViewLayer.aovs.remove by adding a new RNA function to call
the internal BKE_view_layer_remove_aov.
Resolves#99259
Pull Request: blender/blender#105646
