platform support

[hef]

closes #241

[hef]

relevant to containerbase/base#47

[hef]

This should also help make renovatebot/renovate#9229 solvable.

[viceice]

I need some more time to think about it. Currently we only push a new image when the if has changed. For multi platform builds it makes that a lot more complicated. We should publish platform suffixed images first and then a image list manifest containing all platforms. This should only happen if image IDs change. Otherwise the release timestamp of our images will move constantly. We don't like that default docker push behavior that's why we implemented it like it is now.

Maybe we need to accept those changes to have more simplified builds with buildx (bake).

Another this we first need it to update the containerbase binary prebuilds. They need to build the arm binaries before we can build any docker images for arm.

[viceice]

see #241 for required implementation features