OAPI: add mass-task-refresh option to SocketIO job updates

Add `JobUpdate.refresh_tasks` property, to signal to SocketIO clients that
the job update is so big, all the job's tasks should be refreshed.

This is much faster than sending individual task updates one by one.

pkg/api/flamenco-manager.yaml

@@ -1236,7 +1236,13 @@ components:
         "previous_status": { $ref: "#/components/schemas/JobStatus" }
         "type": { type: string }
         "priority": { type: integer, default: 50 }
-      required: [id, updated, status, type, priority]
+        "refresh_tasks":
+          type: boolean
+          description: >
+            Indicates that the client should refresh all the job's tasks. This
+            is sent for mass updates, where updating each individual task would
+            generate too many updates to be practical.
+      required: [id, updated, status, type, priority, refresh_tasks]
 
     SocketIOTaskUpdate:
       type: object