Heartbeat in progress output

Often cerbero's output gets "stuck" for a long time (many many minutes) around the 99% mark, e.g. like this:

or

It would be nice if cerbero could detect that it hasn't output anything for a while and print a list of still-ongoing jobs every 30 seconds or every minute or so.

When I say "a long time" I mean something in the order of 27 minutes or so where we currently don't provide any output at all: