vendor: Updated `k8s.io/system-validators` to `v1.12.1`. The cgroups validator now throws an error instead of a warning if cgroups v1 is detected on the host and the provided KubeletVersion is `v1.35` or newer.
  
  kubeadm: Started using `k8s.io/system-validators` `v1.12.1` in `kubeadm` `v1.35`. During `kubeadm init`, `kubeadm join`, and `kubeadm upgrade`, the SystemVerification preflight check throws an error if cgroups v1 is detected and the detected `kubelet` version is `v1.35` or...

- Added new `CRDValidationRatcheting` alpha feature. During a PATCH or UPDATE Validation Ratcheting discards errors thrown by unchanged portions of the resource from most OpenAPI schema validations. ([#118990](https://github.com/kubernetes/kubernetes/pull/118990), [@alexzielenski](https://github.com/alexzielenski))

- Kubeadm: the deprecated kube-dns is no longer supported as an option. If "ClusterConfiguration.dns.type" is set to "kube-dns" kubeadm will now throw an error. ([#99646](https://github.com/kubernetes/kubernetes/pull/99646), [@rajansandeep](https://github.com/rajansandeep)) [SIG Cluster Lifecycle]

- Kubeadm: avoid panicing if the user has malformed the kubeconfig in the cluster-info config map to not include a valid current context. Include proper validation at the appropriate locations and throw errors instead. ([#134723](https://github.com/kubernetes/kubernetes/pull/134723), [@neolit123](https://github.com/neolit123)) [SIG Cluster Lifecycle]

- kubeadm: Added better handling of errors during unmount when calling `kubeadm reset`. When failing to unmount directories under `/var/run/kubelet`, kubeadm will now throw an error instead of showing a warning and continuing to clean up said directory. In such situations, it is better for you to inspect the problem and resolve it manually. Then, you can call `kubeadm reset` again to complete the cleanup.

- Kubeadm: avoid panicing if the user has malformed the kubeconfig in the cluster-info config map to not include a valid current context. Include proper validation at the appropriate locations and throw errors instead. ([#134725](https://github.com/kubernetes/kubernetes/pull/134725), [@neolit123](https://github.com/neolit123)) [SIG Cluster Lifecycle]

* kubeadm: add a preflight check that throws a warning if the cgroup driver for Docker on Linux is not "systemd" as per the k8s.io CRI installation guide. ([#73837](https://github.com/kubernetes/kubernetes/pull/73837), [@neolit123](https://github.com/neolit123))

- Kubeadm: avoid panicing if the user has malformed the kubeconfig in the cluster-info config map to not include a valid current context. Include proper validation at the appropriate locations and throw errors instead. ([#134724](https://github.com/kubernetes/kubernetes/pull/134724), [@neolit123](https://github.com/neolit123)) [SIG Cluster Lifecycle]

* Kubeadm no longer throws an error for the --cloud-provider=external flag. ([#58259](https://github.com/kubernetes/kubernetes/pull/58259), [@dims](https://github.com/dims))