Room list notifications tweaks

[stefanceriu]

• Remove the "Current" room list activity visibility feature flag option by merging it with "Show"
• Introduce a new "Show unread notification count" feature flag to display the number of unread messages on the notification (green) badges.

Fixes #6101

[github-actions]

PR Checks

• ⚠️ You seem to have made changes to views. Please consider adding screenshots.

[codecov]

Codecov Report

❌ Patch coverage is 93.54839% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 74.98%. Comparing base (4355307) to head (d93c1f8).
⚠️ Report is 1 commits behind head on develop.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
...perOptionsScreen/View/DeveloperOptionsScreen.swift	0.00%	2 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #6106   +/-   ##
========================================
  Coverage    74.98%   74.98%           
========================================
  Files          829      829           
  Lines        58857    58875   +18     
========================================
+ Hits         44131    44149   +18     
  Misses       14726    14726           

Flag	Coverage Δ
unittests	65.44% <93.54%> (+0.01%)	⬆️

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