[DAB RBAC] Re-implement system auditor as a singleton role in new system (#14963)

* Add new enablement settings from DAB RBAC

* Initial implementation of system auditor as role without testing

* Fix system auditor role, remove duplicate assignments

* Make the system auditor role managed

* Flake8 fix

* Remove another thing from old solution

* Fix a few test failures

* Add extra setting to disable custom system roles via API

* Add test for custom role prohibition

awx/api/generics.py

@@ -971,7 +971,6 @@ class CopyAPIView(GenericAPIView):
             None, None, self.model, obj, request.user, create_kwargs=create_kwargs, copy_name=serializer.validated_data.get('name', '')
         )
         if hasattr(new_obj, 'admin_role') and request.user not in new_obj.admin_role.members.all():
-            new_obj.admin_role.members.add(request.user)
             give_creator_permissions(request.user, new_obj)
         if sub_objs:
             permission_check_func = None