Add user status to DM rooms in the room list

[dbkr]

Inspiration taken from #34161 but sanitised

Also:

• Moves emoji validation to fetchUserStatus
• Adds a few tsdoc comments

Checklist

• I have read through review guidelines and CONTRIBUTING.md.
• Tests written for new code (and old code if feasible).
• New or updated public/exported symbols have accurate TSDoc documentation.
• Linter and other CI checks pass.
• I have licensed the changes to Element by completing the Contributor License Agreement (CLA)

[dbkr]

I debated whether it was worth abstracting this away into a class that just gets and emits updates for a single user's status (like the useUserStatus hook but for view models). I'm not sure it is, partially as we don't have this as a pattern afaik, but it feels like a thing that might come up more often.

[americanrefugee]

LGTM