Deprecate registry images

I'm creating this issue to explore the possibility to stop generating our own Docker images in the container registry and use the ones provided by https://hugomods.com/docs/docker/.

Advantages:

• More advanced CI infrastructure that creates many images with various dependencies installed.
• More architectures out of the box. All image tags support linux/amd64 and linux/arm64. Otherwise, we'd have to support implementations like !196 (closed).
• One less thing to maintain 🙂