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

• Make sure the /etc/kubernetes/manifests directory exists for static pods (reduce journalctl spam on worker nodes).
• Added initialization of KUBECONFIG environment variable.
• 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 the image supports legacy and uefi bios (secure boot is not supported).
• prepull-images - pre pull openstack/cni container images.
• npd - added node-problem-detector systemd service on every node.