This should have been added and handles twisted use cases such as:
  1. Install bt5 with ZODB Component C1 using version_priority V1.
  2. Install another bt5 adding version_priority V1.
  3. Install Portal Type using C1 as type_class.
  => No reset was done after 2., so C1 was not added to ZODB Component
     registry_dict (__registry_dict) and thus ignored.