[WIP] Gate DistributedOptimizers on RPC availability (#62774)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/62774
Gates DistributedOptimizer which relies on RRef based on if RPC is available. This should enable ZeRo to work with Windows as Windows should not try to import the DIstributedOptimizer. If this works as expected we can enable the windows tests for functional/local sgd optimizers as well.
ghstack-source-id: 135216642
Test Plan: CI
Reviewed By: pbelevich
Differential Revision: D30117838
fbshipit-source-id: e6365a910a3d1ca40d95fa6777a7019c561957db
