[JIT] recursively compile class types (#38050)
Summary:
Make it so that non-nn Module classes do not need to be annotated with `torch.jit.script`
Pull Request resolved: https://github.com/pytorch/pytorch/pull/38050
Differential Revision: D21482654
Pulled By: eellison
fbshipit-source-id: 22689e4d7a33f6e1574b9495cff29a1fe6abb910
