Use Devices instead of DeviceIndexes in TensorPipe agent (#57294)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/57294
With the advent of CPUs in the device maps, and to be more generic (e.g., to support AMD GPUs), and to avoid conversions when passing to Future and RRef and such, it's easier to use Devices instead of DeviceIndices. This started by just migrating the TensorPipe agent but the RPC layer is quite intertwined so I had to migrate a lot of stuff.
ghstack-source-id: 127916562
Test Plan: CI
Reviewed By: mrshenli
Differential Revision: D28092733
fbshipit-source-id: 024dcb3648c5898ab13e770413c43958f04f1a8a
