Update Phurl for modular transactions

Summary: Ref T6049. This moves Phurl to modular transactions.

Test Plan: Everything works here, add phurl, edit phurl, use phurl. Test various error states. Left a TODO on the validate dupe keys, not sure how to implement that in modular-land.

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin

Maniphest Tasks: T6049

Differential Revision: https://secure.phabricator.com/D17405