podman: output logs regularly while pulling containers

When pulling big containers, it may take minutes for podman to output anything. This can be problematic as it becomes difficult to know if the machine is still doing anything or if it crashed.

While we don't want to flood the logs, I would suggest that having one line every 30 seconds saying what's the download percentage and how many layers got downloaded would strike the right balance between flooding the logs and wondering if the machine is still running.