Add queue instrumentation

Did you have a concept for how to instrument the queue API? I didn't see anything obvious last I looked, unlike Laravel which fires events as jobs are processed. Might be necessary to alter/override the queue service and/or work on adding instrumentability to core queue?

Yeah I wasn't quite sure how we would go about this.. I think it would require overriding the queue backend or queue factory for the producer side, and the same or perhaps Cron::processQueues() for the consumer part.

I'd like to see it built in to core - presumably by dispatching events - so no overriding would be necessary. So next step could be to file a core feature request

These would be my proposed events to enable instrumenting:

When an item is added to a queue: ItemQueuing, ItemQueued

When a queue item is being processed: ItemProcessing, ItemExceptionOccurred, ItemProcessed

It looks like Drush has its own queue runner code, so would need to duplicate the event dispatching code?