[workflows] Add clang-format workflow (#35239)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/35239
This commit adds a new GitHub workflow that checks if a pull request
has any formatting issues using `tools/clang_format.py`.
Testing:
Literally in prod.
Test Plan: Imported from OSS
Reviewed By: eellison
Differential Revision: D20605802
Pulled By: SplitInfinity
fbshipit-source-id: 8dd6517dd907d7b6a3d9e9dd3969b666fbebb709
