[PyTorch] Add Enum to IValue Deepcopy (#69937)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/69937
This enables ```export_torch_mobile_model``` compatibility with Enum IValues
Test Plan: ModuleAPITest.DeepCopyEnum
Reviewed By: gmagogsfm
Differential Revision: D33104681
fbshipit-source-id: ca2a6d259c312487fe38dd1bed33ab6b7910bc2a
