runner autoscaler - always keep x amount of spare runners

[gacopl]

I would love to have ability when using autoscaler in polling mode, to always keep like 2 extra idle runners available to make sure new jobs start fast.

Currenlty MinReplicas will make it fast for only the first job, any subsequent jobs if previous ones are still running will have to wait for cluster to scale-out

Maybe there is a way to achieve that with Mixed Polling and Runner Busy ??