Events for the users to understand what's going on with their WPA

[alok87]

We have often see developer telling us the problems going on with WPA and then the first way to debug the issue is by going through WPA kubernetes logs for the queue to find what is going on. We should logs events for all the important thing that goes on with the WPA object.

Reasons:

1. Easy to debug.
2. Developer who does have access to wpa logs but has access to their WPA object can troubleshoot problems on their own.

Examples

• Say if the queue specified does not exist, logs error, but does not log events.
• Cases where scale up is happening slow, developer should be able to see their WPA queue activity history to measure the scaling times. lastScaleupTime, idleSince