Reduce supported kubernetes versions to match kubernetes releases lifetime

The Kubernetes project maintains release branches for the most recent three minor releases (1.37, 1.36, 1.35). https://kubernetes.io/releases/

Minikube supports 6 versions (1.37, 1.36, 1.35, 1.34, 1.33, 1.32). This is not possible even if we had big team since versions become EOL (e..g at this time version 1.33 and older are EOL.

Since we missed the 1.36 release, and we still test oldest version with 1.28, we support now 9 versions (1.37, 1.36, 1.35, 1.34, 1.33, 1.32, 1.31, 1.30, 1.29, 1.28).

People that want to test older version can use older minikube version.

Change the policy to supporting 3 versions: 1.37, 1.36, 1.35.

Tasks:

• Set oldest version to 1.35
• Trim kubernetes versions lists, keeping 3 minor versions
• When updating kubernetes version, drop the oldest version (when default becomes 1.38, drop 1.35)
• Stop building preloads for older releases (Job is not part of minikube)