chore: update ESLint to v9 and apply code style changes

[susnux]

• closes chore(deps-dev): Bump eslint from 8.57.1 to 9.39.1 #900

Update to ESLint v9 and applied the needed changed.
See individual commits why something had to be changed.

[codecov]

Codecov Report

❌ Patch coverage is 95.23810% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 98.46%. Comparing base (819bf77) to head (2c21193).
⚠️ Report is 7 commits behind head on main.

Files with missing lines	Patch %	Lines
lib/ConsoleLogger.ts	95.23%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #907      +/-   ##
==========================================
+ Coverage   98.38%   98.46%   +0.07%     
==========================================
  Files           4        4              
  Lines          62       65       +3     
  Branches       13       13              
==========================================
+ Hits           61       64       +3     
  Partials        1        1              

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[max-nextcloud]

Thanks a lot for taking care of this! ❤️