Summary:
Lint related fixes: Improve internal/OSS consistency. Fix the fight between black and certain pyre-ignore markers by moving them to the line before.
Use clang-format-8 automatically if present. Small number of pyre fixes.
arc doesn't run pyre at the moment, so I put back the explicit call to pyre. I don't know if there's an option somewhere to change this.
Reviewed By: nikhilaravi
Differential Revision: D19780518
fbshipit-source-id: ef1c243392322fa074130f6cff2dd8a6f7738a7f
