Add more debug logging around code loading

[davidjgoss]

🤔 What's changed?

Add more logger.debug statements when loading each user-authored file for the support code library.

⚡️ What's your motivation?

This may help us narrow down issues with loading, see #2353.

🏷️ 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.

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[coveralls]

coverage: 98.392% (+0.005%) from 98.387%
when pulling 6b9df2c on more-debug-logging
into 7df2c9b on main.