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/sql/manage_storage.php

@@ -99,14 +99,9 @@ try {
   exit(1);
 }
 
-$workflows = array(
-  new PhabricatorStorageManagementDatabasesWorkflow(),
-  new PhabricatorStorageManagementDestroyWorkflow(),
-  new PhabricatorStorageManagementDumpWorkflow(),
-  new PhabricatorStorageManagementStatusWorkflow(),
-  new PhabricatorStorageManagementProbeWorkflow(),
-  new PhabricatorStorageManagementUpgradeWorkflow(),
-);
+$workflows = id(new PhutilSymbolLoader())
+  ->setAncestorClass('PhabricatorStorageManagementWorkflow')
+  ->loadObjects();
 
 $patches = PhabricatorSQLPatchList::buildAllPatches();