Create OS images using toolchain rather than copying and modifying existing OS images

[JonasBchrt]

Creating new OS images by copying old OS images introduces some risks, e.g.

• divergence of the code in an OS image and the code an GitHub
• undocumented modifications of the code or settings on the OS image
• issues with reproducibility
• requiring sharing of large image files
• trackability of problems and their origins
  To tackle this, we could use a toolchain to build OS images every time we make changes, e.g., https://github.com/RPi-Distro/pi-gen (It also has a github action version).