Set ActionName to "Created" for PhabricatorTransactions::TYPE_CREATE

Summary:
Explicitly set "Created" as ActionName (to be used as a mail subject line vary prefix) when the transaction type is `PhabricatorTransactions::TYPE_CREATE` to avoid falling back to a generic "Updated" prefix.

Closes T15865

Test Plan: Either create a new task and check the mail subject line prefix (if you have a mail setup in your Phorge instance), or use the debug patch in P45 and check the order of action strengths.

Reviewers: O1 Blessed Committers, valerio.bozzolan

Reviewed By: O1 Blessed Committers, valerio.bozzolan

Subscribers: tobiaswiese, valerio.bozzolan, Matthew, Cigaryno

Maniphest Tasks: T15865

Differential Revision: https://we.phorge.it/D25732

src/applications/transactions/storage/PhabricatorApplicationTransaction.php

@@ -1608,6 +1608,8 @@ abstract class PhabricatorApplicationTransaction
         return pht('Changed Policy');
       case PhabricatorTransactions::TYPE_SUBSCRIBERS:
         return pht('Changed Subscribers');
+      case PhabricatorTransactions::TYPE_CREATE:
+        return pht('Created');
       default:
         return pht('Updated');
     }