Return messages in definition order

[davidjgoss]

🤔 What's changed?

SupportCodeLibrary.toEnvelopes() now maintains the original definition order of all support code, rather than first grouping into types. It does this by capturing the order in the builder and carrying that state through to the library.

⚡️ What's your motivation?

cucumber/compatibility-kit#213

🏷️ What kind of change is this?

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

📋 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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