Add a workflow and a new config option for locking authentication providers

Summary:
Ref T7667. Adds new flows bin/auth lock and bin/auth unlock to prevent compromised administrator accounts from doing additional damage by altering the authentication provider configuration.

Note that this currently doesn't actually do anything because we aren't checking this config key in any of the edit controllers yet.

Test Plan: Ran lock and unlock, checked for correct DB state, observed expected setup warning.

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin

Maniphest Tasks: T7667

Differential Revision: https://secure.phabricator.com/D20394