Modernize OAuthServer PHIDs and Queries

Summary:
  - Modernize PHID types.
  - Implement `PhabricatorPolicyInterface`.
  - Make queries policy aware.

Test Plan: Browsed client and authorization lists.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: chad, epriestley

Differential Revision: https://secure.phabricator.com/D8560