[proposal] More responsive Pod States Informer

[saintube]

What is your proposal:

There are scenarios in which we want the Koordlet to retrieve the up-to-date pod states from the Kubelet via the statesInformer. However, the current pod statsInformer is only notified by the pod creation and timer, which means the pod update events like the change of the labels and annotations are ignored.

Here we want to enhance the responsiveness of the Koordlet's statesInformer. The Koordlet should know the pod updates and retrieve the pod states in time. Furthermore, a pod update callback should be added to notify the other modules that rely on the pod metadata.

Why is this needed:

Is there a suggested solution, if so, please add it: