upgrade Kubernetes patch versions 1.28.9, 1.27.13, 1.26.15

This MR:

• upgrades the patch version for Kubernetes to use 1.28.9, 1.27.13 and 1.26.15
• integrates a suitably recent diskimage-builder version to have OS images for those k8s versions (thanks to sylva-projects/sylva-elements/diskimage-builder!203 (merged))
• updates ingress-nginx and calico versions to keep in sync with what RKE2 uses for those k8s patch versions (this required a minor refactoring of k8s-version-match named template) -- those versions come from:
  • https://github.com/rancher/rke2/blob/v1.28.9%2Brke2r1/charts/chart_versions.yaml
  • https://github.com/rancher/rke2/blob/v1.27.13%2Brke2r1/charts/chart_versions.yaml
  • https://github.com/rancher/rke2/blob/v1.26.15%2Brke2r1/charts/chart_versions.yaml
• updates image_keys and sylva_diskimagebuilder_images accordingly in environment values