CI: add multiarch build / tagging

Adds initial draft of multiarch capability.

For finishing this up we have to:

• add a build runner with following specs to the container-library group (send me the token via Matrix or Signal or whatever :)
• add multiarch features to si shell tooling (interface proposal within draft)

A first successful multiarch on SI-Infrastructure, AWS and Quay.io can be found here https://git.shivering-isles.com/w4tsn/python-mqtt-gpio-container/-/jobs/8563

Runner Specs:

Description: containers-aarch64-autoscale
Tags: aarch64, arm64, armv8, autoscale, aws, ec2, fedora, podman, s3, selinux
Type: docker+machine