[RFE] Support rebuilding CAPI images in Azure Community Gallery without changing Flatcar and Kubernetes version

[invidian]

Current situation

With #1265, we run into an issue with CAPI images, where rebuilding with a certain image-builder patch would help delivering working images to users again. However, this requires removal of current images from the community gallery and rebuilding them, which is not optimal (ideally artifacts should be append-only, as their checksums will change and it makes it hard to track when images gets updated etc etc.).

Impact

Delivering image-builder patches requires removal of existing images, which is undesired.

Ideal future situation

Images with image-builder updates can be made easily available to users, without a need for removal of existing images.

Implementation options

We could add a build number (e.g. incremented sequentially when required) to CAPI images to be able to deliver image-builder patches when needed. This is similar to what distro packages are doing with changes to build system or when packages are rebuilt because their dependencies has been updated.

So names like flatcar-stable-amd64-capi-v1.26.11 would become flatcar-stable-amd64-capi-v1.26.11-1 and with image-builder patch, new image would become flatcar-stable-amd64-capi-v1.26.11-2.