Transform 'customized-images.yaml' into separate repos.

[piontec]

customized-images.yaml are the only difference between retagger and upstream skopeo.
We want to get rid of this feature, as it makes "customized" images:

• completely incompatible with future security extensions (signing)
• hard to track in terms of ownership.

As such, they have to be migrated into proper separate repositories, with owners and full CI process.

[uvegla]

POC: https://github.com/giantswarm/laszlo-monorepo

Images are built with architect so they are pushed to the usual registries and then mirrored via the normal methods.

You can add new images with: https://github.com/giantswarm/laszlo-monorepo/blob/main/add-new-image.sh

See:

• https://gigantic.slack.com/archives/C02MS174K/p1722438110077769
• https://gigantic.slack.com/archives/C056D9YQ1B5/p1722415572704209