Fix bug in process_group_name when there is duplicate pgs (#100518)
Summary: with the new c10d API, we don't need all ranks to call new_group. Integrate with the new API, so that every rank just call new_group 3 times, with a local barrier with the members within the group.
Reviewed By: xunnanxu, eeggl
Differential Revision: D45315615
Pull Request resolved: https://github.com/pytorch/pytorch/pull/100518
Approved by: https://github.com/kumpera
