Remove faulty process group agent logic (#62409)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/62409
This a reland of #61907 because removing process_group_agent.h / cpp broke facebook specific tests. I will remove the files and update the internal test code in a separate PR.
Test Plan: Imported from OSS
Reviewed By: mrshenli
Differential Revision: D29990001
Pulled By: H-Huang
fbshipit-source-id: 2ee333322247d8b72691152308c3297e8c0c006d
