MatrixRTC: fix different devices from the same user overwriting the room info state event.

[toger5]

With the new event format we have one event per device (not one event per user). Consequently it does not make a lot of sense to store the state events in the room info using the user id as the keys for the Map of state events.

Instead a tuple of userId and deviceId is used.

• Public API changes documented in changelogs (optional)

Signed-off-by:

[codecov]

Codecov Report

Attention: Patch coverage is 96.55172% with 1 line in your changes missing coverage. Please review.

Project coverage is 84.11%. Comparing base (711a753) to head (abc617f).
Report is 241 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/matrix-sdk-base/src/rooms/mod.rs	95.83%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3867      +/-   ##
==========================================
+ Coverage   84.09%   84.11%   +0.02%     
==========================================
  Files         262      262              
  Lines       27646    27656      +10     
==========================================
+ Hits        23249    23263      +14     
+ Misses       4397     4393       -4     

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[toger5]

superseded by: #3972