Ability to configure --node-cidr-mask-size into kube-controller-manager

[robermorales]

Given that some CNI providers like Cilium can read the Node CIDR provisioned by kube-controller-manager, this PR makes a great option to configure a higher ipv4 pool for pods inside every node, just by allowing this flag to be exposed from the manifests.

Including this snippet inside a kops manifest a user can get a mask size for pods different than /24, and so an effective maxPods limit over the default 150. Cilium is only an example in this snippet. The option is generally available and documented in kube-controller-manager.

...
  kubelet:
    maxPods: 4096
  kubeControllerManager:
    nodeCIDRMaskSize: 20
  networking:
    cilium: {}
...

Thanks for considering.

[mikesplain]

/ok-to-test

[justinsb]

Thanks @robermorales

/approve
/lgtm

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: justinsb, robermorales

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[mikesplain]

/test pull-kops-e2e-kubernetes-aws

[mikesplain]

This should be fixed now

/test pull-kops-e2e-kubernetes-aws