[Gradient Compression] Provide 2 default C++ comm hooks (#46701)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/46701
Provide 2 built-in implementations of C++ comm hook.
Original PR issue: C++ DDP Communication Hook https://github.com/pytorch/pytorch/issues/46348
ghstack-source-id: 115319061
Test Plan: waitforbuildbot
Reviewed By: pritamdamania87
Differential Revision: D24382504
fbshipit-source-id: 1c1ef56620f91ab37a1707c5589f1d0eb4455bb3
