Taint bootstrap kubelet and drain the node before shutting down self-hosted kubelet

[invidian]

To avoid the impact of configuration drift between self-hosted and bootstrap kubelet, it make sense for bootstrap kubelet to only handle self-hosted kubelet pod. All other pods should be then handled with self-hosted kubelet.

This way, if bootstrap kubelet does not have certain option configured (e.g. host mount), it won't affect the pod needing it (for example when mounting PVCs)

We could make bootstrap kubelet register with extra taint, which then self-hosted kubelet should remove after it's ready.

The same way, on shutdown of self-hosted kubelet, we could use PreStop hook to taint and drain the node. That ensures that updating self-hosted kubelet is safe and has a small impact on the cluster.