Bring CodeQL GitHub Actions workflow more in line with defaults

[charmander]

Newer defaults and not permissions I intentionally removed, I think?

[github-advanced-security]

This pull request sets up GitHub code scanning for this repository. Once the scans have completed and the checks have passed, the analysis results for this pull request branch will appear on this overview. Once you merge this pull request, the 'Security' tab will show more code scanning analysis results (for example, for the default branch). Depending on your configuration and choice of analysis tool, future pull requests will be annotated with code scanning analysis results. For more information about GitHub code scanning, check out the documentation.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (0971e69) 59.62% compared to head (f4a5eef) 59.62%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1388   +/-   ##
=======================================
  Coverage   59.62%   59.62%           
=======================================
  Files          94       94           
  Lines        9068     9068           
  Branches     1635     1635           
=======================================
  Hits         5407     5407           
  Misses       3227     3227           
  Partials      434      434           

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