Cleanup PT-D imports (#85781)
Summary:
The flow logic around torch.dist imports results in large number of pyre errors (100's); would be preferable to just raise on importing as opposed to silently fail.
Con: Some percentage (MacOS?) of users may have notebooks that imports PT-D, although would think small, since any attempt to call parts of the library would just fail...
TODO: assuming ok, will remove the 10's-100's of unused pyre ignores no longer required.
Test Plan: existing unit tests
Differential Revision: D39842273
Pull Request resolved: https://github.com/pytorch/pytorch/pull/85781
Approved by: https://github.com/mrshenli
