[LTC] Upstream class BackendDevice (#68027)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/68027
This commit upstreams class BackendDevice to the master, which is a backend
specific representation of the actual hardware, for instances, CPU, GPU, or
TPU.
This concept is important for backend like XLA where it needs to tell the
actual hardware type from the c10::DeviceType::Lazy virtual device during
both IR constructions and lowerings.
Test Plan: ./build/bin/test_lazy --gtest_filter=BackendDeviceTest.*
Reviewed By: wconstab
Differential Revision: D32261838
Pulled By: alanwaketan
fbshipit-source-id: 579c3fc5f9da7847c887a383c6047e8ecb9cc5bc
