Add options to pin unread/mentioned rooms to the top of the room list

[turt2live]

Fixes element-hq/element-web#6604
Fixes element-hq/element-web#732
Fixes element-hq/element-web#1104
Fixes element-hq/element-web#7319

[dbkr]

@lukebarnard1 you might want to take a look at this is your room list store stuff. From my PoV

• I dislike that this logic for room ordering is now split between here (the component) and RoomListStore.
• Surely a sort function would make more sense here, rather than making separate lists of rooms with unread / notifications, de-duplicating them then concatenating them?

Edit: have also commented on element-hq/element-web#732

[turt2live]

Originally there was a sort in there, however the sort gets complicated due to the tri-state nature: mentioned, notified (unread), and unread. Having the fused list makes it a little easier to understand in my opinion.

[lukebarnard1]

I dislike that this logic for room ordering is now split between here (the component) and RoomListStore.

Two stores updating the same view isn't the worst thing in the world, I don't think. In this case the settings store isn't fluxy but the model still roughly holds.

Having said that, the RoomListStore already imports a lot of stuff and there's a _recentsComparator that this could be done in. And there's something to be said about keeping all the sorting logic in the same place.

[bwindels]

@turt2live UserSettings.js is conflicting with develop.

[turt2live]

@bwindels thanks. Should be good now