Bump Kubernetes to v1.28

[twz123]

Tracking issue for the 1.28 update. The alphas are out and the release is planned for mid of august.

• Ship quay.io/k0sproject/kube-proxy:v1.28.1
  k0sproject/image-builder#44
• Check Helm / controller-runtime compatibility
  Currently, it "just compiles" ...
• Check for any API version removals
  Nothing, as it seems: https://github.com/kubernetes/kubernetes/blob/master/CHANGELOG/CHANGELOG-1.28.md#deprecation
• Update metrics-server to v0.6.3
  Upstream has done the same
  Bump metrics-server to v0.6.4 #3395
• Update to controller-runtime 0.16
  Bump sigs.k8s.io/controller-runtime from 0.15.0 to 0.16.2 #3479
  Apparently not a hard requirement, but cleaning up remnants from the last minor version bump seem reasonable ...
• Ensure all features targeted for 1.28 land in main before cutting the release
  • 1.28 Milestone
• Create new release branch
• Add new backport/release-1.28 label to GitHub
• Update https://k0sproject.io with the 1.28 version number
  Update supported k8s versions k0sproject.github.io#32
• Upload conformance test logs to cncf/k8s-conformance
  Conformance results for v1.28/k0s cncf/k8s-conformance#2849
• Whatever else may be lurking in the upstream release ...

[github-actions]

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