Make all bin/* scripts locate their workflows dynamically

Summary:
Ref T2015. Not directly related to Drydock, but I bumped into this. All these scripts currently enumerate their workflows explicitly.

Instead, use `PhutilSymbolLoader` to automatically discover workflows. This reduces code duplication and errors (see all the bad `extends` this diff fixes) and lets third parties add new workflows (not clearly valuable?).

Test Plan: Ran `bin/x help` for each modified script.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T2015

Differential Revision: https://secure.phabricator.com/D7840

scripts/repository/manage_repositories.php

@@ -15,16 +15,8 @@ EOSYNOPSIS
   );
 $args->parseStandardArguments();
 
-$workflows = array(
-  new PhabricatorRepositoryManagementPullWorkflow(),
-  new PhabricatorRepositoryManagementDiscoverWorkflow(),
-  new PhabricatorRepositoryManagementEditWorkflow(),
-  new PhabricatorRepositoryManagementListWorkflow(),
-  new PhabricatorRepositoryManagementDeleteWorkflow(),
-  new PhabricatorRepositoryManagementMarkImportedWorkflow(),
-  new PhabricatorRepositoryManagementLookupUsersWorkflow(),
-  new PhabricatorRepositoryManagementImportingWorkflow(),
-  new PhutilHelpArgumentWorkflow(),
-);
-
+$workflows = id(new PhutilSymbolLoader())
+  ->setAncestorClass('PhabricatorRepositoryManagementWorkflow')
+  ->loadObjects();
+$workflows[] = new PhutilHelpArgumentWorkflow();
 $args->parseWorkflows($workflows);