Add `bin/auth list-factors` and `bin/auth strip` to remove multi-factor auth

Summary:
Ref T4398. The major goals here is to let administrators strip auth factors in two cases:

  - A user lost their phone and needs access restored to their account; or
  - an install previously used an API-based factor like SMS, but want to stop supporting it (this isn't possible today).

Test Plan:
  - Used `bin/auth list-factors` to show installed factors.
  - Used `bin/auth strip` with various mixtures of flags to selectively choose and strip factors from accounts.
  - Also ran `bin/auth refresh` to verify refreshing OAuth tokens works (small `OAuth` vs `OAuth2` tweak).

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T4398

Differential Revision: https://secure.phabricator.com/D8909