Add warning on ProcessGroup and ProcessGroup::Work APIs (#46220)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/46220
Test Plan: Imported from OSS
Reviewed By: gmagogsfm
Differential Revision: D24294437
Pulled By: gmagogsfm
fbshipit-source-id: 198f8e5760beeb1d18740f971647d2537afb3dd6
