Emit messages for suggestions

[davidjgoss]

🤔 What's changed?

Emit suggestion messages with snippets when an undefined step is encountered.

Before this, snippets sat entirely within the formatters area. We now use the same mechanism in the runner layer to emit the messages, but what happens in formatters is unchanged. We could rework the formatters model to just have them consume the suggestion messages and work with those, but I'd rather just skip that as we'll ultimately be replacing the existing formatters with message-based ones anyway.

⚡️ What's your motivation?

cucumber/common#2272

🏷️ What kind of change is this?

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

---

This text was originally generated from a template, then edited by hand. You can modify the template here.

[coveralls]

coverage: 97.808% (+0.03%) from 97.782%
when pulling ca08df6 on suggestions-messages
into 1e0bc64 on main.