Kubeadm: Automate certificate copy between control planes in HA setups

- Joining control plane nodes to a HA cluster can now be simplified by enabling the optional automatic copy of certificates from an existing control plane node.
- You can now use `kubeadm init --experimental-upload-certs` and `kubeadm join --experimental-control-plane --certificate-key`.
kubernetes/kubeadm: [#1373](https://github.com/kubernetes/kubeadm/issues/1373)

    routePlanner.defaultConnectionIdleAtNanos = expireSooner

    // Turn it into an http/2 connection that supports 5 concurrent streams
    // which can satisfy a larger policy
    val connection = routePlanner.plans.first().connection
    val http2Connection = connectHttp2(peer, connection, 5)
    setPolicy(pool, address, AddressPolicy(5))
    assertThat(pool.connectionCount()).isEqualTo(1)

- Kubeadm: only taint control plane nodes when the legacy "master" taint is present. This avoids the bug where "kubeadm upgrade" will re-taint a control plane  node with the new "control plane" taint even if the user explicitly untainted the node. ([#109840](https://github.com/kubernetes/kubernetes/pull/109840), [@neolit123](https://github.com/neolit123))

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ControlPlaneKubeletLocalMode feature gate. It can be used to tell kubeadm to use the local kube-apiserver endpoint for the kubelet when creating a cluster with "kubeadm init" or when joining control plane nodes with "kubeadm join".  The "kubeadm join" workflow now includes two new experimental phases called "control-plane-join-etcd" and "kubelet-wait-bootstrap" which will be used when the feature gate is enabled. This phases will be marked as non-experimental when ControlPlaneKubeletLocalMode becomes GA. During...

* kubeadm: Remove hard-coded default version when fetching stable version from the web fails. Fixes [kubeadm 1.6.1 deploying 1.6.0 control plane](https://github.com/kubernetes/kubeadm/issues/224). ([#43999](https://github.com/kubernetes/kubernetes/pull/43999), [@mikedanese](https://github.com/mikedanese))

- github.com/bufbuild/protovalidate-go: [v0.9.1](https://github.com/bufbuild/protovalidate-go/tree/v0.9.1)
- github.com/envoyproxy/go-control-plane/envoy: [v1.32.4](https://github.com/envoyproxy/go-control-plane/tree/envoy/v1.32.4)
- github.com/envoyproxy/go-control-plane/ratelimit: [v0.1.0](https://github.com/envoyproxy/go-control-plane/tree/ratelimit/v0.1.0)
- github.com/go-jose/go-jose/v4: [v4.0.4](https://github.com/go-jose/go-jose/tree/v4.0.4)

are hence enabled by default. This will be fixed in a future release.
[#38593](https://github.com/kubernetes/kubernetes/issues/38593)
* Federation control plane can be upgraded by updating the image
fields in the `Deployment` specs of the control plane components.
However, federation control plane upgrades were not tested in this
release [38537](https://github.com/kubernetes/kubernetes/issues/38537)

## Notable Changes to Existing Behavior

- Restores priority of static control plane pods in the cluster/gce/manifests control-plane manifests ([#89970](https://github.com/kubernetes/kubernetes/pull/89970), [@liggitt](https://github.com/liggitt)) [SIG Cluster Lifecycle and Node]


# v1.18.1

* Action required: If you have a running federation control plane, you will have to ensure that for all federation resources, the corresponding namespace exists in federation control plane. ([#31139](https://github.com/kubernetes/kubernetes/pull/31139), [@nikhiljindal](https://github.com/nikhiljindal))