Fix findTestStepsStartedBy coverage and JS

[davidjgoss]

🤔 What's changed?

The method variant findTestStepsStartedBy(TestCaseFinished) has no test coverage in Java and didn't exist in JavaScript. This PR remedies both of these by extending the acceptance test and then updating the JavaScript implementation so it passes.

🏷️ What kind of change is this?

• 🐛 Bug fix (non-breaking change which fixes a defect)

♻️ Anything particular you want feedback on?

I'm not quite sure I've followed the pattern right with the acceptance tests - @mpkorstanje?

📋 Checklist:

• I agree to respect and uphold the Cucumber Community Code of Conduct
• I've changed the behaviour of the code
  • I have added/updated tests to cover my changes.
• 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.

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