base: sort the heroes in the computed display name alphabetically

[bnjbvr]

This ensures the room name is deterministic, when it's computed client-side. Includes regression tests too, where the members or heroes might not be in the expected order.

[codecov]

Codecov Report

Attention: Patch coverage is 95.23810% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 82.92%. Comparing base (2987bd1) to head (16aa8c6).
Report is 4 commits behind head on main.

Files	Patch %	Lines
crates/matrix-sdk-base/src/rooms/normal.rs	94.11%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3377   +/-   ##
=======================================
  Coverage   82.92%   82.92%           
=======================================
  Files         245      245           
  Lines       24894    24897    +3     
=======================================
+ Hits        20643    20646    +3     
  Misses       4251     4251           

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[andybalaam]

Makes sense, thanks!

[Hywan]

(wrongly sent the review before)

[Hywan]

Approving ahead of time to avoid back and forth during the review process.