AKS worker nodes: support for Ubuntu 22.04 LTS

The kernel version in 18.04 is just to old, I need a newer kernel version for mainline SGX support and others seem to require 20.04 as well:
https://github.com/Azure/AKS/issues/2706
https://github.com/Azure/AKS/issues/2829
https://github.com/Azure/AKS/issues/1579