Summary: Ref T5655. Fixes T6849. This is another take on D11131, which was missing the DB migration and was reverted in rP7c4de0f6be77ddaea593e1f41ae27211ec179a55.
Test Plan: Ran `./bin/storage upgrade` and verified that the classes were renamed in the `phabricator_policy.policy` table.
Reviewers: #blessed_reviewers, epriestley
Reviewed By: #blessed_reviewers, epriestley
Subscribers: Korvin, epriestley
Maniphest Tasks: T6849, T5655
Differential Revision: https://secure.phabricator.com/D11166
