Generalize printing of the hook results

[slarse]

There's currently quite a bit of hard coding going on in the printing of the hook results. As more and more commands are getting hooks, it's about time this becomes more generalized. Currently, it looks like this:

repobee/src/_repobee/cli/dispatch.py

Lines 58 to 68 in 182df3e

	if is_ext_command or args.action in [
	plug.cli.CoreCommand.repos.setup,
	plug.cli.CoreCommand.repos.update,
	plug.cli.CoreCommand.repos.clone,
	]:
	if hook_results:
	plug.echo(formatters.format_hook_results_output(hook_results))
	if hook_results and "hook_results_file" in args and args.hook_results_file:
	_handle_hook_results(
	hook_results=hook_results, filepath=args.hook_results_file
	)

Ugly to say the least. If the outer if that constrains printing hook results to a few commands is removed, some stuff that we don't want to print is printed (see #699). This is just poorly designed. I think the easiest way to solve this is to:

1. Standardize the hook results format. It's a bit ad-hoc at the moment.
2. Add metainfo somewhere about what to print.