Re-factor the EventBus to use Map/Set internally

[Snuffleupagus]

Especially the Array to Set conversion should be helpful, since adding/removing elements from a Set is more efficient.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.98%. Comparing base (ce4ff55) to head (0d5df9d).
⚠️ Report is 2 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #21673   +/-   ##
=======================================
  Coverage   89.97%   89.98%           
=======================================
  Files         263      263           
  Lines       66901    66896    -5     
=======================================
  Hits        60196    60196           
+ Misses       6705     6700    -5     

Flag	Coverage Δ
browsertest	66.53% <0.00%> (-0.02%)	⬇️
integrationtest	69.32% <100.00%> (-0.01%)	⬇️
unittest	57.82% <100.00%> (-0.01%)	⬇️
unittestcli	56.54% <100.00%> (-0.03%)	⬇️

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[timvandermeij]

Thank you for simplifying this!