✨ Allow to disable KubeProxy and CoreDNS

[sathieu]

What this PR does / why we need it:

Disabling kube-proxy using controlplane.cluster.x-k8s.io/skip-kube-proxy annotation is not enough because kubeadm will try to pull the kube-proxy image on preflight.

The proper way to disable kube-proxy is to use Proxy.Disable=true, as in this PR.

Which issue(s) this PR fixes:
Related to #12288

/area provider/bootstrap-kubeadm

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by:
Once this PR has been reviewed and has the lgtm label, please assign enxebre for approval. For more information see the Code Review Process.

The full list of commands accepted by this bot can be found here.

Needs approval from an approver in each of these files:

• OWNERS

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[k8s-ci-robot]

Hi @sathieu. Thanks for your PR.

I'm waiting for a kubernetes-sigs member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

I understand the commands that are listed here.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.