Fix T73170: New Scene -> "Full Copy" Crashes Blender.

rBac723db57fd8ba5 makes proper remapping of all pointers in Scene...
including the object pointers of bases in ViewLayers.

Using `BKE_main_collection_sync_remap()` makes sense here anyway
(compared to `BKE_main_collection_sync()`, it additionally clears caches
in ViewLayers and Collections), this whole code makes a lot of
remapping.

Note that I do not really understand *why* that was working OK
before rBac723db57fd8ba5. I.E. *why* not remapping at all ViewLayers'
base object pointers seemed to be OK...

This whole collection/viewlayer caching is very hard to follow, and
really needs a full rework at some point (just as much as ID copying
code in general, and scene copying code in particular, in fact).

source/blender/editors/object/object_relations.c

@@ -1802,7 +1802,7 @@ static void single_object_users(
 
   /* Making single user may affect other scenes if they share
    * with current one some collections in their ViewLayer. */
-  BKE_main_collection_sync(bmain);
+  BKE_main_collection_sync_remap(bmain);
 }
 
 /* not an especially efficient function, only added so the single user