`UnversionedKubeletConfigMap` feature gate to Beta and enabled the feature by default. This implies that 1) for new clusters kubeadm will start using the `kube-system/kubelet-config` naming scheme for the kubelet ConfigMap and RBAC rules, instead of the legacy `kubelet-config-x.yy` naming. 2) during upgrade, kubeadm will only write the new scheme ConfigMap and RBAC objects. To disable the feature you can pass `UnversionedKubeletConfigMap: false` in the kubeadm config for new clusters. For upgrade on existing clusters...

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    <_comment>Scala source code</_comment>
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    <_comment>Scheme source code</_comment>
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    <_comment>Sed code</_comment>

### API-Machinery

* Fixed webhooks to use the scheme provided in clientConfig, instead of defaulting to http. ([#60943](https://github.com/kubernetes/kubernetes/pull/60943), [@jennybuckley](https://github.com/jennybuckley))

- 'Container `preStop` and `postStart` lifecycle handlers using `httpGet` now
  honor the specified `scheme` and `headers` fields. This enables setting custom
  headers and changing the scheme to `HTTPS`, consistent with container
  startup/readiness/liveness probe capabilities. Lifecycle handlers configured
  with `scheme: HTTPS` that encounter errors indicating the endpoint is actually