Kubernetes version support and testing

[viceice]

Currently we test all version from v1.27 to v1.30, which are 4 versions. We should make a note that we only test the latest 4 versions.

So when v1.31 comes, we'll drop v1.27 to not overload ci. We can still support older kubernet versions on a community supported best effort.

We can still run older kubeval tests as they are fast ( ~10s ). We do so with v1.26 to 1.30.

We could also test the oldest and the newest 3 supported versions to reduce load.

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• https://docs.aws.amazon.com/eks/latest/userguide/kubernetes-versions.html#kubernetes-release-calendar
• https://learn.microsoft.com/en-us/azure/aks/supported-kubernetes-versions?tabs=azure-cli#aks-kubernetes-release-calendar
• https://cloud.google.com/kubernetes-engine/docs/release-schedule

[kvanzuijlen]

Actually, I wrote a little tool in Golang to do this. I'm still working on adding a GitHub Action for it (to automatically generate matrixes). The CLI tool can currently look up versions from Docker and return the N most recent versions (so basically what I was looking for with renovatebot/renovate#26489). I've posted the tool to GitHub today over at https://github.com/kvanzuijlen/version. Let me know if you'd be open to using this tool once I've added some unit tests and added a GitHub Action.

Edit: I'm also planning on adding support for GitHub tags and GitHub releases

[viceice]

@kvanzuijlen Feel free to open a PR to test the tool 🤗