Automatic merge from submit-queue
[Refactor] QOS to have QOS Class type for QoS classes
This PR adds a QOSClass type and initializes QOSclass constants for the three QoS classes.
It would be good to use this in all future QOS related features.
This would be good to have for the (Pod level cgroups isolation proposal)[https://github.com/kubernetes/kubernetes/pull/26751] that i am working on aswell.
@vishh PTAL
Signed-off-by: Buddha Prakash <buddhap@google.com>