Fix issue with room duplication caused by filtering and selecting room using keyboard

[t3chguy]

Wrap sticky room updates in lock to prevent setStickyRoom running in middle of setKnownRooms

Fixes the most common reproductions of element-hq/element-web#14508 but likely not all

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So I reproduced this 100% of the time when filtering room list and selecting the room using keyboard.
The difference this has is it also clears the filter at the same time.
This makes two events race in the RoomListStore:

• Updating the sticky room to the one you selected
• The setKnownRooms calculating values for the new (unfiltered) list

This issue came about from when the filtering was split into prefiltering and runtime filtering as prior to that the filters were applied later.

In theory a mutex around the critical path in setKnownRooms solves this.
I can no longer reproduce it using the steps which reproduced it 100% of the time for me.
This is much less invasive than #6024
But there is a significant likelihood that other reproduction methods for the same symptoms may still be possible given this is just one race and the RoomListStore is rather complex and has too much async logic.

[t3chguy]

Hmm, it looks like 75% of the async nature of the RLS is due to it making the SortAlgorithm async even though its probably fast enough to just be blocking, might make another PR with a different approach which is likely more bulletproof but might not scale to accounts like M's

[dbkr]

Looks like a sensible workaround but yeah, agreed - the fact that stuff is async for no immediate reason is a bit terrifying.

[t3chguy]

Succeeded by #6391