Stop using loadRelationships in differential related herald adapters

Summary:
Used DifferentialRevisionQuery with the relevant need*() calls in the test controller.
And started assuming the revision has reviewers and CC phids in HeraldDifferentialRevisionAdapter.

Test Plan:
Added herald rules that use revisions (one for revisions another for commit) and reviewers.
Created, accepted and landed a revision that matched the rules and checked all rules were applied.

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin

Maniphest Tasks: T1279

Differential Revision: https://secure.phabricator.com/D6468

Conflicts:
src/applications/herald/adapter/HeraldCommitAdapter.php
src/applications/herald/adapter/HeraldDifferentialRevisionAdapter.php
src/applications/herald/controller/HeraldTestConsoleController.php