run: handle parse errors better

[davidjgoss]

🤔 What's changed?

Don't throw immediately when a parse error is encountered by gherkin - instead ensure all the errors (as well as any valid sources) are emitted and do a normal cleanup and exit.

Avoided making this part of parseGherkinMessageStream because that's on the public API (for now) and I didn't want to make a breaking change to its signature unnecessarily.

⚡️ What's your motivation?

Fixes #1404.

Previously we'd throw on the first parse error and formatters wouldn't have a chance to do anything with it before the process exited.

🏷️ What kind of change is this?

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

♻️ Anything particular you want feedback on?

📋 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.

[coveralls]

Coverage increased (+0.006%) to 98.274% when pulling 1264859 on feat/emit-parse-error into 36ccc1b on main.

[aurelien-reeves]

Looks good 👌

Just a small request to rename the new step definition, but this is an approval 💪