Explore buildah in place of kaniko

https://buildah.io/

Buildah is an OCI image builder by the same team who builds podman. It's worth exploring if we can get any benefits using buildah in place of kaniko.

Start by reviewing the Buildah material at https://buildah.io/ and comparing it with the repository's current Kaniko use. The issue names no files, tests, or entry points, so first locate that integration and determine what benefits, compatibility requirements, and migration scope would need evaluation before a change can be considered done.

索引モデルが issue の本文から書いたものです。