CI: Simplify job structure

[stotko]

Our CI job structure contains a lot of repetitions and is requires quite a lot of maintenance to keep it up to date. Simplify the structure:

• Unify workflows:
  • Ubuntu + Windows -> Tests
  • Analysis + Style -> Lint
• Add dependabot to periodically check for updates
• Add jobs to check if all jobs in a workflow succeeded
• Allow canceling jobs to speed up the re-runs

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (43c0785) 97.33% compared to head (427e4dc) 97.33%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #404   +/-   ##
=======================================
  Coverage   97.33%   97.33%           
=======================================
  Files          31       31           
  Lines        2512     2512           
=======================================
  Hits         2445     2445           
  Misses         67       67           

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