[RPC] Support timeout in rref._get_type() (#50498)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/50498
This change is mostly needed for the next diff in this stack, where
rref._get_type() is called in the rpc_async/rpc_sync RRef proxy function and
can block indefinitely if there is no timeout. It will also be useful to have a
timeout argument when we publicize this API to keep it consistent with other
RPC APIs.
ghstack-source-id: 119859767
Test Plan: Added UT
Reviewed By: pritamdamania87
Differential Revision: D25897588
fbshipit-source-id: 2e84aaf7e4faecf80005c78ee2ac8710f387503e
