When a project has a custom icon, use that icon to label the project policy in the policy dropown

Summary:
Fixes T8808. Currently, all project use the default ("Briefcase") project icon when they appear in a policy dropdown.

Since project policies are separated out into a "Members of Projects" section of the dropdown anyway, there is no reason not to use the actual project icon, which is often more clear.

Test Plan: {F6849927}

Maniphest Tasks: T8808

Differential Revision: https://secure.phabricator.com/D20799

src/applications/policy/storage/PhabricatorPolicy.php

@@ -85,8 +85,10 @@ final class PhabricatorPolicy
     $phid_type = phid_get_type($policy_identifier);
     switch ($phid_type) {
       case PhabricatorProjectProjectPHIDType::TYPECONST:
-        $policy->setType(PhabricatorPolicyType::TYPE_PROJECT);
-        $policy->setName($handle->getName());
+        $policy
+          ->setType(PhabricatorPolicyType::TYPE_PROJECT)
+          ->setName($handle->getName())
+          ->setIcon($handle->getIcon());
         break;
       case PhabricatorPeopleUserPHIDType::TYPECONST:
         $policy->setType(PhabricatorPolicyType::TYPE_USER);