chore: update GitHub Actions version and remove xvfb

[mister-ben]

Updates actions to address GitHub's Node 16 deprecation.

Updating codecov to v4 hopefully improves the reliability uploading. This change means contributors wanting codecov in their forks need to add a CODECOV_TOKEN secret to their repository with their codecov token.

Removes the xvfb action as avfb is available by default on ubuntu in GitHub Actions.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 83.49%. Comparing base (8e5870f) to head (991ce58).
Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #8682      +/-   ##
==========================================
+ Coverage   82.85%   83.49%   +0.64%     
==========================================
  Files         113      113              
  Lines        7647     7647              
  Branches     1839     1839              
==========================================
+ Hits         6336     6385      +49     
+ Misses       1311     1262      -49     

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