[1.8.x] Refs #24354 -- Prevented repointing of relations on superclasses when...

[1.8.x] Refs #24354 -- Prevented repointing of relations on superclasses when migrating a subclass's name change

The issue was hidden on 1.8+ until #24573 due to a bug inside the model
reloading process.

Forwardport of patch from ae87ad00