feat(spaces): reuse existing room display name computation logic for spaces

[stefanceriu]

This PR add a new public static method on the base-sdk's Room that allows computing room display names with much of the same logic as real rooms but from discrete values.

[codspeed-hq]

CodSpeed Performance Report

Merging #5752 will not alter performance

_{Comparing stefan/spaceDisplayNames (a420a81) with main (7fbc414)}

Summary

✅ 50 untouched

[codecov]

Codecov Report

❌ Patch coverage is 98.88889% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 88.43%. Comparing base (d01a28c) to head (a420a81).
⚠️ Report is 14 commits behind head on main.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
crates/matrix-sdk-ui/src/spaces/room.rs	94.11%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5752   +/-   ##
=======================================
  Coverage   88.43%   88.43%           
=======================================
  Files         360      360           
  Lines       99624    99712   +88     
  Branches    99624    99712   +88     
=======================================
+ Hits        88103    88185   +82     
- Misses       7393     7398    +5     
- Partials     4128     4129    +1     

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