Add hash and equality operators for WorkerInfo (#29958)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/29958
DistributedOptimizer relies on hashing WorkerInfo in order to coalesce fan-out RPCs. This will likely be a very common use case (EASGD will do the same, for example).
ghstack-source-id: 94169198
Test Plan: unit test.
Differential Revision: D18548257
fbshipit-source-id: 7d67d4e1b9bc60403c372164982a75ae8c1d8389
