Allow deletion of a node (True deletion API)

[mpw96]

Which component are you using?:
cluster-autoscaler

Is your feature request designed to solve a problem? If so describe the problem this feature should solve.:
During a maintenance window I need to quickly move workload away from a workergroup with minimal service disruption for the customer. I also want to control the resource overhead. I want to taint (all nodes of) a workergroup and drain a couple of them. When draining them is finished, I'd like to drain the next chunk and so on.

Describe the solution you'd like.:
I'd like to be able (after draining a node) to delete it or have "someone" delete it. The most natural solution for me would be to just allow kubectl delete node some-node without the creation of some replacement node after some time. At the moment this does not work (see FAQ of cluster autoscaler and machine-controller-manager).

Describe any alternative solutions you've considered.:
Another solution would be something like setting an annotation on the node resource that tells Gardener, that I want to have this node deleted.

Additional context.:
Had a discussion with @dguendisch @rishabh-11 and others already.

[rishabh-11]

/close
Not required at the moment by the stakeholders

[vlerenc]

Reason being, you can help around the initial problem with (e.g.):

   clusterAutoscaler:
      scaleDownDelayAfterAdd: 0s
      scaleDownDelayAfterDelete: 0s
      scaleDownDelayAfterFailure: 3m0s
      scaleDownUnneededTime: 30s
      scaleDownUtilizationThreshold: 0.5
      scanInterval: 10s
      expander: priority
      maxNodeProvisionTime: 6m0s
      maxGracefulTerminationSeconds: 600
      newPodScaleUpDelay: 0s
      maxEmptyBulkDelete: 10