docs: add Kubernetes upgrading guide

docs/launchpad/guides/kubeadm-upgrading.md

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+# Upgrading Kubernetes with kubeadm
+
+In this guide we will use as an example upgrading from kubernetes v1.28.1 to v1.28.3
+
+The the control-plane nodes must be upgraded first, followed by the worker nodes.
+
+## Upgrade Control-Plane Nodes
+
+Pick a control-plane node to be the first to upgrade, followed by:
+
+**1:** Upgrading kubeadm and kubectl to the latest patch version of the desired major version:
+```bash
+apt-get update
+apt-mark unhold kubeadm
+apt-get install -y kubeadm='1.28.3-*'
+apt-mark hold kubeadm
+```
+
+**2:** Verify the upgrade plan:
+```bash
+kubeadm upgrade plan v1.28.3
+```
+
+**3:** Drain the node:
+```
+kubectl drain <node-name> --ignore-daemonsets
+```
+
+**4:** Perform the upgrade:
+```bash
+kubeadm upgrade apply v1.28.3
+```
+**5:** Upgrade the node's CRI-O or other container runtime to an appropriate version if need be. For CRI-O that would be changing the minor version in the repositories added to `/etc/apt/sources.list.d` and then running:
+```bash
+apt-get update
+apt-get install cri-o cri-o-runc
+systemctl daemon-reload
+systemctl restart crio
+```
+
+**6:** Upgrade kubelet and kubectl
+```bash
+apt-get update
+apt-mark unhold kubelet
+apt-mark unhold kubectl
+apt-get install -y kubelet='1.28.3-*'
+apt-get install -y kubectl='1.28.3-*'
+apt-mark hold kubelet
+apt-mark hold kubectl
+```
+
+**7:** Restart kubelet
+```bash
+systemctl daemon-reload
+systemctl restart kubelet
+```
+
+**8:** Uncordon the node
+```
+kubectl uncordon <node-name>
+```
+
+**9:** Possibly, upgrade CNI. Particularly if it's a minor version upgrade there may be a need to update the CNI to a new version as well according to the vendor's release notes for the upgrade process
+
+For the remaining control-plane nodes, execute steps 1 to 8, one at a time but:
+
+- step 2 is skipped, no need to plan the upgrade anymore
+- step 4 is replaced by:
+```bash
+kubeadm upgrade node
+```
+
+## Upgrade Worker Nodes
+
+After all the control-plane nodes are upgraded, it's time to upgrade your worker nodes by following the previous steps from 1 to 8 but:
+- step 2 is skipped
+- step 4 is replaced by:
+```bash
+kubeadm upgrade node
+```
+
+*Note*: You can upgrade as many worker nodes in parallel as you see fit and/or find adequate to your availability requirements, as the nodes being upgraded will be drained from workloads.