Add type annotations to torch._C._distributed_rpc module. (#46624)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/46624
Test Plan: Imported from OSS
Reviewed By: glaringlee
Differential Revision: D24761656
Pulled By: xuzhao9
fbshipit-source-id: b55aee5dd2b97f573a50e5bbfddde7d984943fec
