Allow Herald to add package reviewers

Summary: Ref T10939. Packages are valid reviewers, so let Herald "Add Reviewers" and "Add Blocking Reviewers" actions add them.

Test Plan:
  - Wrote a rule to add package reviewers.
  - Hit the rule, saw a package reviewer added, viewed transcript.

{F1311731}

{F1311732}

{F1311733}

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T10939

Differential Revision: https://secure.phabricator.com/D15917

src/applications/differential/herald/DifferentialReviewersAddBlockingReviewersHeraldAction.php

@@ -22,7 +22,7 @@ final class DifferentialReviewersAddBlockingReviewersHeraldAction
   }
 
   protected function getDatasource() {
-    return new PhabricatorMetaMTAMailableDatasource();
+    return new DiffusionAuditorDatasource();
   }
 
   public function renderActionDescription($value) {

src/applications/differential/herald/DifferentialReviewersAddReviewersHeraldAction.php

@@ -22,7 +22,7 @@ final class DifferentialReviewersAddReviewersHeraldAction
   }
 
   protected function getDatasource() {
-    return new PhabricatorMetaMTAMailableDatasource();
+    return new DiffusionAuditorDatasource();
   }
 
   public function renderActionDescription($value) {

src/applications/differential/herald/DifferentialReviewersHeraldAction.php

@@ -69,6 +69,7 @@ abstract class DifferentialReviewersHeraldAction
     $allowed_types = array(
       PhabricatorPeopleUserPHIDType::TYPECONST,
       PhabricatorProjectProjectPHIDType::TYPECONST,
+      PhabricatorOwnersPackagePHIDType::TYPECONST,
     );
 
     $targets = $this->loadStandardTargets($phids, $allowed_types, $current);