WIP: Buildah/podman support

[Baenimyr]

Add support for buildah to create and publish images.

The buildah build command with the --manifest option is used to build an image. The buildah manifest push command sends the images to a remote registry and retrieve the digest (use a random tag like docker).

Options example in sources:

buildah:
  pull: true
  target: "app"
  platforms:
    - linux/amd64
    - linux/arm64
  buildArgs:
    VERSION: latest
  rawOptions:
    - --layers
    - --jobs=0
    - --quiet

The user can use rawOptions to add arguments like --layers, --jobs=0 or --cache-from. None of them is activated by default.

• [x] build
• [x] push to destinations
• [x] get digest and let kbld create more tags
• [x] create tests