Controller should retain priority by default

[alvaroaleman]

We introduced a priority queue that by default de-prioritizes events if the object was unchanged. If the object gets requeued, it will lose that priority. We should:

• Make the controller check if the workqueue is a priority queue
• If yes, store the priority a given key has
• If yes, re-use that priority when calling Add, AddRatelimited or AddAfter

Related to #2374

[sbueringer]

Makes sense