Summary:
Pass Process Group Name and Desc to NCCL communicator in order to access pg information in NCCL layer.
The information is passed as commDesc string(i.e. "<pg_desc>:<pg_name>")
Function only valid when NCCL_COMM_DESCRIPTION is defined.

Differential Revision: D55703310

Pull Request resolved: https://github.com/pytorch/pytorch/pull/124149
Approved by: https://github.com/shuqiangzhang