* Migrate FStaticCustomVersionRegistry::Lock to use FTransactionallySafeRWLock.
* Disable caching of FUnversionedStructSchema when in a closed transaction.
* Ensure that the loader logic of StaticDuplicateObjectEx() is done in the open.
* Allocate PrimitiveSceneIds in the open.
#rb Brandon.Schaefer, michael.nicolella
[CL 35735509 by ben clayton in ue5-main branch]