Remove `THFile`, `THDiskFile`, and `THMemoryFile` (#37830)
Summary:
Fix https://github.com/pytorch/pytorch/issues/36996
Remove seemingly unused files.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/37830
Differential Revision: D21431969
Pulled By: mruberry
fbshipit-source-id: 824fa86f03ce0049ceddb093468800154ae8048b
