Add noop-event to Change stream

When you listening changeStream for collection with rare updates, you have not any knowledge about:

• you don't reciving event because nothing happens or somethins broken?
• what processing events delay do you have (you can get unpredictable delay on changeStream resuming)?

Also you can't update refresh token without receiving changeStream event.

So, I think should be some `noop` event for changeStream (optional or with configurable period).