Check and support upgrades

[makhov]

Check, and if needed, support k0s version updates for RemoteMachine's and other k0smotron scenarios

[nekwar]

Current sequence of actions that need to be performed in order to upgrade child k0s cluster with k0smotron as Control Plane Bootstrap provider:

1. Create configmap with Autopilot's Plan with controllers only as targets. Example:

   apiVersion: v1
   kind: ConfigMap
   metadata:
   name: example-cluster-autopilot-plan
   namespace: default
   data:
   data: |
   apiVersion: autopilot.k0sproject.io/v1beta2
   kind: Plan
   metadata:
     name: autopilot
   spec:
     id: id1234
     timestamp: now
     commands:
       - k0supdate:
           version: v1.29.1+k0s.1
           platforms:
             linux-amd64:
               url: https://github.com/k0sproject/k0s/releases/download/v1.29.1+k0s.1/k0s-v1.29.1+k0s.1-amd64
           targets:
             controllers:
               discovery:
                 selector: {}

2. Add this configmap to ClusterResourceSet (the easiest way to do it is to use kubectl edit clusterresourceset <crs-name>)
3. Wait for controllers to be upgraded
4. Change version in spec.k0sVersion in K0sControlPlane resource (this needs to be done in order to new controllers, if there will be any, to have new k0s version)

Once controllers are upgraded, you can proceed with workers upgrade:

1. Change k0s version in K0sWorkerConfigTemplate
2. Change version in MachineDeployment

Issues, that need to be addressed

• Logically, when you're changing version in MachineDeployment, it should also change it in K0sWorkerConfigTemplate (because MachineDeployment is the owner for K0sWorkerConfigTemplate) so you don't have to change versions in two different places