Fixed new_group won't work for two or more different rank groups (#14529)

Fixed new_group won't work for two or more different rank groups (#14529)

Summary:
This fixed two things:

(1) NCCL group doesn't support 2 or more groups, this is because, we need a group name in ProcessGroupNCCL class to keep track of the ProcessGroup ID within that group name, and also the NCCL unique ID within that group name and process group ID.  Otherwise, different processes will create different NCCL PG in different orders and can clash on these names.  This will fix the NCCL problem.

(2)  When using new_group, each rank should enter this function and update its global group name counter to ensure that every rank always operates on the same group name.

With both fixes: repro code in: https://github.com/pytorch/pytorch/issues/14528 should work with both NCCL and Gloo backends.

```
tengli@learnfair096:~$ python -m torch.distributed.launch --nproc_per_node=8 --nnodes=1 --node_rank=0 --master_addr=127.0.0.1 --master_port=30000 ~/github_issues/nccl_group.py
rank: 0 - val: 6.0
rank: 2 - val: 6.0
rank: 3 - val: 6.0
rank: 1 - val: 6.0
rank: 4 - val: 22.0
rank: 6 - val: 22.0
rank: 5 - val: 22.0
rank: 7 - val: 22.0
```
Pull Request resolved: https://github.com/pytorch/pytorch/pull/14529

Differential Revision: D13253434

Pulled By: teng-li

fbshipit-source-id: 8eb45882b996b06d951fc9a306d5de86a42e8b84