Add ufmt linter/formatter (#246)

Summary:
Pull Request resolved: https://github.com/pytorch/executorch/pull/246

Enable ufmt formatter so that we can replicate BLACK and USORT

Following these steps

https://www.internalfb.com/intern/wiki/Python/code_formatting/pyfmt/

https://fb.workplace.com/groups/pythonlinters/posts/684192797083133/?comment_id=684215477080865&reply_comment_id=684217327080680

Reviewed By: larryliu0820, dbort

Differential Revision: D49076476

fbshipit-source-id: da161e8404e25a95bb60780434dbdddc54ef496d