Renaming parent invalidates childs hierarchy

When renaming the Parent of a Child Blueprint it invalidates the hierarchy of the Child Blueprint and nests its components under the DefaultSceneRoot.

This bug was reported in 4.19.2 (CL-4033788) and reproduced in 4.18.3 (CL-3832480), 4.20 Preview 3 (CL-4135216), and Main 4.21 (CL-415470)

1. In any 4.19.2 project create two Blueprint Actors where one inherits from the other (Parent/Child)
2. In the Parent Blueprint add two sets of nested Scene Components
3. In the Child Blueprint add on to the second set of nested Scene Components
4. Rename the Parent Blueprint

Result: The child's hierarchy gets invalidated, and all non inherited components move under the default scene root.

Expected: The child hierarchy remains the same.