Improve kubernetes version check

[ludusrusso]

If I try to create or update a TPC with a non existing minor version of kubernetes, the CRD API call succede but the tcp remain in an provisioning state.

How to reproduce:

apiVersion: kamaji.clastix.io/v1alpha1
kind: TenantControlPlane
metadata:
  name: non-existing-version
  namespace: default
spec:
  controlPlane:
    deployment:
      replicas: 1
    service:
      serviceType: ClusterIP
  kubernetes:
    version: "v1.25.90" # <- non existing version
    kubelet:
      cgroupfs: cgroupfs
    admissionControllers:
      - ResourceQuota
      - LimitRanger
  networkProfile:
    port: 6443
  addons:
    coreDNS: {}
    kubeProxy: {}

Expected behavior

Get an error similar to the one obtained with a non existing major version

admission webhook "vtenantcontrolplane.kb.io" denied the request: unable to upgrade to a version greater than the supported one, actually 1.26.0

[prometherion]

Unfortunately, the single way to address this is to hard-code all the available versions of Kubernetes.

This would require more maintenance toil, and it could a technical debt in the future where we could specify a different image repository mirror or any different Kubernetes distribution (although not yet supported).

I summon @bsctl to have his insights about UX.