R1:aa483738899d

Update `bin/auth` MFA commands for the new "MFA Provider" indirection layer

Summary:
Ref T13222. This updates the CLI tools and documentation for the changes in D19975.

The flags `--type` and `--all-types` retain their current meaning. In most cases, `bin/auth strip --type totp` is sufficient and you don't need to bother looking up the relevant provider PHID. The existing `bin/auth list-factors` is also unchanged.

The new `--provider` flag allows you to select configs from a particular provider in a…