ci(run-tests): refactor run-tests.sh and add linter checks

[tiborsimko]

• Refactors run-tests.sh to add usage help, standardise function naming, and improve option handling.
• Adds new linter and formatter checks where applicable (yamllint, shfmt, markdownlint, prettier, jsonlint).
• Updates .github/workflows/ci.yml with corresponding CI jobs.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 41.14%. Comparing base (5e92a2f) to head (06cd6ab).
⚠️ Report is 6 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #516   +/-   ##
=======================================
  Coverage   41.14%   41.14%           
=======================================
  Files          28       28           
  Lines        2066     2066           
=======================================
  Hits          850      850           
  Misses       1216     1216           

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