fix: end html formatter stream at appropriate time

[davidjgoss]

🤔 What's changed?

In the html formatter, change when we end the CucumberHtmlStream that pipes to the output stream.

Previously we did this when we saw a testRunFinished message, which sort of makes sense. However there are other ways for a test run to end e.g. Gherkin parse failure as in the linked issue. This meant we were awaiting a stream to finish that was never going to, and this caused the process to just exit (I'm a little hazy as to exactly why, but I could reproduce it).

Now we only end the stream in the cleanup step after the test run has finished (or an error has caused us to bail out of it) and it works for both cases - covered by existing scenarios for the happy path and a new one covering the parse failure.

⚡️ What's your motivation?

Fixes #2225.

🏷️ What kind of change is this?

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

📋 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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[coveralls]

Coverage: 98.563% (-0.002%) from 98.564% when pulling 41eec86 on fix/html-formatter-parse-failure into 6f3385c on main.