Add NCCL work sequence number to work info (#120596)
Summary: Expose sequence number to work info. The number can help applications identify a NCCL work more precisely.
Test Plan:
1. pytest test/distributed/test_c10d_nccl.py::WorkHookTest::test_on_completion_hook_seq
2. pytest test/distributed/test_c10d_nccl.py::WorkHookTest
Differential Revision: D54180050
Pull Request resolved: https://github.com/pytorch/pytorch/pull/120596
Approved by: https://github.com/kwen2501
