In preparation for T274599: Allow uncollapsing grouped results we should clean up existing code to make sure we have as little duplication as possible. That task should only need to add the core functionality once, with only the rendering logic implemented twice for the two different displays.
T286141: Make watchlistUtils non-static covers making watchlistUtils into a non-static class WatchlistUtils, which we can then put some more logic in, but there are other things that don't have to wait for that