[Dart] Update lint config to be stricter & resolve new violations

[Fried-man]

🤔 What's changed?

• I updated dart\analysis_options.yaml to have the content of very_good_analysis' configuration for Dart 3.7 (analysis_options.8.0.0.yaml) & added an ignore for generated dart source.
• I ran dart fix --apply to automatically apply known lint resolutions to the code.
• I updated the example's output from print to standard out to satisfy the newly found lint violation.

⚡️ What's your motivation?

Per @olexale's comment, the linter configuration we currently have is quite relaxed. In order to drive community adoption of cucumber_messages & improve code quality, the linter has been updated to reflect the contents of the most popular non-google lint configuration.

Previously, @mpkorstanje cited, in a pr review comment, that we should not introduce an additional dependency for the linter. This solution allows for no new dependency to be introduced, the linter to be significantly stricter, and for this repo to have explicit control over the analyzer configuration.

🏷️ What kind of change is this?

• 🏦 Refactoring/debt/DX (improvement to code design, tooling, etc. without changing behaviour)

♻️ Anything particular you want feedback on?

Feedback on if this is the right approach.

📋 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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