Add a _RemoteDevice structure for ShardedTensor/ShardingSpec. (#62927)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/62927
As part of the ShardedTensor work, we realized we do need some sort of
_RemoteDevice structure that deals with our format of "workername/device" so
that users don't have to worry about parsing this string directly.
Right now this structure is just the bare minimum and is mostly a container for
describing a remote device. It is currently only used in ShardedTensor,
ShardingSpec and RemoteModule.
Once we actually have a consolidated remote device proposal, this class can be
extended appropriately if needed.
ghstack-source-id: 135534086
Test Plan:
1) unit tests
2) waitforbuildbot
Reviewed By: SciPioneer
Differential Revision: D30170689
fbshipit-source-id: 1ac2e81c7a597dc40bf3fbf2c1168c382c66649f