Add pybind type caster for c10::Device (#57292)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/57292
In Future (and soon in other places too) we need to receive a list of devices from Python-land. We don't want to just take their indices because we need full devices in order to infer the type from them. torch.device is not defined through pybind, it's defined through a plain `PyModule_AddObject` call with CPython, thus pybind isn't naturally able to understand and convert it. However we can provide a custom type caster which fixes that. We have this already for at::Tensor, at::Generator, ...
ghstack-source-id: 127916268
Test Plan: CI
Reviewed By: mrshenli
Differential Revision: D28092732
fbshipit-source-id: 1c31d0b85a4d5c9e7bde8161efbb7574d505157c
