Improved argument parsing.

[przemyslaw-zan]

🚀 Summary

ckeditor5-dev-tests-run-automated and ckeditor5-dev-tests-run-manual will now point the user to the --help argument when an unknown argument is parsed, then exit process with code 1.

ckeditor5-dev's internal test script was also improved in the same way. Also added --help and --files argument which allows running only specified packages, instead of all of them.

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💡 Testing

• Setup ckeditor5-dev within ckeditor5 on the branch ci/4355. Attempt to run both manual and automatic tests with real and fake arguments.
• Run pnpm run test within ckeditor5-dev with real and fake arguments.

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