[PyTorch] Add Device_test.cpp (#63203)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/63203
Currently, `c10::Device` isn't being tested - i.e. there's no test to ensure that the device string parsing works as expected. This diff adds very basic tests to assert that the stuff we expect to work works, and the stuff that we don't expect to work doesn't work.
ghstack-source-id: 136006962
Test Plan:
New test. Ran as:
```
cd fbsource/fbcode/
buck test //caffe2/c10:c10_test_0 -- -r '.*DeviceTest.*'
```
Reviewed By: dreiss, raziel
Differential Revision: D30286910
fbshipit-source-id: b5699068dcbba89d5d224dbaf74b175f3f785a00
