Support enabling/disabling pushers (from MSC3881) (#13799)

Partial implementation of MSC3881

synapse/_scripts/synapse_port_db.py

@@ -111,6 +111,7 @@ BOOLEAN_COLUMNS = {
     "e2e_fallback_keys_json": ["used"],
     "access_tokens": ["used"],
     "device_lists_changes_in_room": ["converted_to_destinations"],
+    "pushers": ["enabled"],
 }