Add sequence number support for UCC (#85047)
Add sequence number support for UCC, mostly following format of ProcressGroupNCCL.
Pass new test: `test_all_gather_object_subgroup`
Add skips for gather tests: `test_gather_object` and `test_gather_object_subgroup`
cc @mrshenli @pritamdamania87 @zhaojuanmao @satgera @rohan-varma @gqchen @aazzolini @osalpekar @jiayisuse @H-Huang @kwen2501 @awgu
Pull Request resolved: https://github.com/pytorch/pytorch/pull/85047
Approved by: https://github.com/kwen2501
