Maintain position in room list buffer

Something I find frustrating is when I switch from the room list buffer to a room buffer, and then `q`uit back to the room list, and find that point has been moved back to the start of the room list. This resetting seems to happen a lot.

(Edit: I see that `ement-room-list-auto-update` is relevant here; with that disabled, it looks like the issue doesn't occur. It would be nice to get the best of both worlds, though.)

I think the buffer is actually being erased and regenerated, so it's presumably not quite as trivial as a save-excursion; but to me it's an undesirable UX to have the apparent position forcibly changed this way. Even if the buffer is being rebuilt, I think it would be beneficial to try to match the previous position based on context. As it's a room list, "the line of the same room" would seem pretty easy and reliable in most cases.