Dynamically update supported Kubernetes versions

[paulphys]

Currently the available Kubernetes versions are hard-coded. Ideally they should be updated regularly based on if they are still supported (https://kubernetes.io/releases/)

Ideas:

• Scrape the supported versions from https://kubernetes.io/releases
• Get the supported versions from the available capi-images

Proposed format:

{
 "1.31": ["1.31.0", "1.31.1"],
 "1.30": ["1.30.0", "1.30.1", "1.30.2", "1.30.3", "1.30.4"],
 ...
}