Kubernetes image build for Magnum ClusterApi driver

Auto build ubuntu kubernetes images for Openstack Magnum Service with a docker.
Ubuntu 24.04 + k8s 1.30+ as base image, tested with Magnum Capi driver.

Notes

• https://github.com/vexxhost/magnum-cluster-api - new Magnum driver supporting ClusterApi.
• https://github.com/vexxhost/capo-image-elements - project to build Kubernetes images.

Fixes

• Fixed build error where systemctl enable containerd/kubelet would throw exception - service does not exist. Fixed by adding element-deps.
• Make sure the /etc/kubernetes/manifests directory exists for static pods (reduce logs on worker nodes).
• cloud-init uses default Openstack datasources (Openstack, ConfigDrive)

Patches

• qemu-ga - added qemu guest agent to image.
• allow-root - allow root user and ssh root access with a key to kubernetes nodes.
• block-device-efi - make sure image works under Legacy and Uefi Bios (secure boot is not supported).