Ensure the room list always triggers updates on itself

[turt2live]

#4164 round two, without tripping all the bear traps that make this code awful to work with. Code is essentially stolen from @t3chguy to make the list stable, and actually update.

The index management stuff from #4164 appears to not be needed and is in fact one of the bear traps in this area.

Rewriting the whole room list store for element-hq/element-web#11743 is still a good idea, but in terms of actually fixing the bug this seems fine enough for now. It also means we can release without putting a block on rewriting the room list.

Fixes element-hq/element-web#12588

Edit: I've also broken out the commits to try and explain in future diffs what the problem was and what it fixes, hopefully.

[t3chguy]

if it works then sure, I had an this exact code at one point (except with a switch-case) and I had an issue where switching between two consecutive rooms it sometimes swapped them wrongly because the alphabetic comparison was done between the wrong entries because of the removal happening before the insertion

[turt2live]

I had an issue where switching between two consecutive rooms it sometimes swapped them wrongly because the alphabetic comparison was done between the wrong entries because of the removal happening before the insertion

This is exactly the description of element-hq/element-web#9216 :D (just with a different algorithm). In the grand scheme of things it's obviously bad, but also less important. Something like element-hq/element-web#11743 would certainly fix it.

[t3chguy]

Ah right true, I guess I was aiming to fix that one in one fell swoop

[turt2live]

yea, I highly don't recommend that. That bug is screaming for a refactor, which I'll still take a look at doing.