[13/n] Extend the return type of RendezvousBackend's set_state method (#57142)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/57142
This PR extends the return type of `RendezvousBackend`'s `set_state` method with an additional boolean flag that specifies whether the write attempt has succeeded.
ghstack-source-id: 127629538
Test Plan: Run the updated unit tests.
Reviewed By: tierex
Differential Revision: D28058980
fbshipit-source-id: 26333790c39386891beb155b20ba1291d2cbdd03
