Ported loadAuxiliaryFields method to differential.query conduit method

Summary: Ported the the loadAuxiliaryfields method from differential.getrevision method to modern conduit differential.query method

Test Plan: Created a test diff in differential to see if nothing has been broken

Reviewers: epriestley

CC: aran, Korvin

Differential Revision: https://secure.phabricator.com/D5230