Migrate Differential revision edges to use modern EdgeType subclasses

Summary: Modernize Differential edges to subclass `PhabricatorEdgeType`. Largely based on D11045.

Test Plan: From previous experience, these changes are fairly trivial and safe. I poked around a little to make sure things looked reasonably okay.

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: Korvin, Krenair, epriestley

Differential Revision: https://secure.phabricator.com/D11074

src/applications/diffusion/controller/DiffusionCommitController.php

@@ -418,7 +418,7 @@ final class DiffusionCommitController extends DiffusionController {
       ->withSourcePHIDs(array($commit_phid))
       ->withEdgeTypes(array(
         DiffusionCommitHasTaskEdgeType::EDGECONST,
-        PhabricatorEdgeConfig::TYPE_COMMIT_HAS_DREV,
+        DiffusionCommitHasRevisionEdgeType::EDGECONST,
       ));
 
     $edges = $edge_query->execute();
@@ -426,7 +426,7 @@ final class DiffusionCommitController extends DiffusionController {
     $task_phids = array_keys(
       $edges[$commit_phid][DiffusionCommitHasTaskEdgeType::EDGECONST]);
     $revision_phid = key(
-      $edges[$commit_phid][PhabricatorEdgeConfig::TYPE_COMMIT_HAS_DREV]);
+      $edges[$commit_phid][DiffusionCommitHasRevisionEdgeType::EDGECONST]);
 
     $phids = $edge_query->getDestinationPHIDs(array($commit_phid));