Add location to pickle

[mpkorstanje]

🤔 What's changed?

⚡️ What's your motivation?

🏷️ What kind of change is this?

• 📖 Documentation (improvements without changing code)
• 🏦 Refactoring/debt/DX (improvement to code design, tooling, etc. without changing behaviour)
• 🐛 Bug fix (non-breaking change which fixes a defect)
• ⚡ New feature (non-breaking change which adds new behaviour)
• 💥 Breaking change (incompatible changes to the API)

♻️ Anything particular you want feedback on?

📋 Checklist:

• Add location to pickle messages#308
• 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.

[mpkorstanje]

Pickles are intended to be processed Cucumber features that can be executed without the AST of a Gherkin document. This is done by removing the syntactic sugar of backgrounds and scenario outlines.

One of the problems I'm running into is that while pickles have an internal id they are externally identified by their uri and line number. For example path/to.feature:3. One example of this is the rerun-format. And to obtain that identity I have to reach back into the AST which is exactly what is not supposed to happen.

This is for now a draft to figure out how much trouble it will cause so I can discuss it with the core team. The matching PR against messages is cucumber/messages#308.