[fx] remove CPatcher (#69032)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/69032
I am removing it because, for packaging-related reasons, it's easier if
torch.fx is a pure Python module.
I don't think there is much reason to keep it: this functionality was
experimental, has no known users currently, and we didn't have a clear
path to turning it on by default due to regressions in tracing
performance. Also, it only was ever enabled for `rand` and friends.
Technically the removal of the `enable_cpatching` arguments on
`symbolic_trace` and `Tracer.__init__` are BC-breaking, but the
docstrings clearly state that the argument is experimental and BC is not
guaranteed, so I think it's fine.
Test Plan: Imported from OSS
Reviewed By: soulitzer
Differential Revision: D32706344
Pulled By: suo
fbshipit-source-id: 501648b5c3610ae71829b5e7db74e3b8c9e1a480
