[GPU] Enable Metal on macosx (#47635)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/47635
Add macosx support for metal. The supported os version is 10.13 and above.
ghstack-source-id: 116845318
Test Plan:
1. Sandcastle Tests
2. CircleCI Jobs
3. In the next diff, we'll run the person segmentation model inside a macos app
Reviewed By: dreiss
Differential Revision: D24825088
fbshipit-source-id: 10d7976c953e765599002dc42d7f8d248d7c9846
