[c10d] Fix object-based collectives for debug mode (#68223)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/68223
DETAIL debug mode didn't work with object-based collectives for NCCL backend, because we'd only check if backend is NCCL and then move tensors to CUDA.
Instead, check if it is a wrapped PG, and then check the pg that is wrapped to see if its nccl.
ghstack-source-id: 143242023
Test Plan: CI
Reviewed By: zhaojuanmao
Differential Revision: D32366840
fbshipit-source-id: be0a2af6849f8f24446593f4a4fbea4a67586ee5
