Add Option to Run Features in Subtests

[joeljr]

🤔 What's changed?

Add Option to run features in separate subtests.

⚡️ What's your motivation?

Usually, scenarios are grouped logically in feature files. Adding this options helps test report readability when running multiple feature files each containing multiple scenarios.

🏷️ What kind of change is this?

• :zap: New feature (non-breaking change which adds new behaviour)

♻️ Anything particular you want feedback on?

Comparing the test results from the added unit tests versus the one running all scenarios.

📋 Checklist:

• [x] I agree to respect and uphold the Cucumber Community Code of Conduct
• [x] I've changed the behaviour of the code
  • [x] I have added/updated tests to cover my changes.
• [x] My change requires a change to the documentation.
  • [ ] I have updated the documentation accordingly.
• [ ] Users should know about my change
  • [ ] I have added an entry to the "Unreleased" section of the CHANGELOG, linking to this pull request.

[joeljr]

Doesn't work with concurrency.