fix: strip script output before logged JSON

[ascorbic]

🔗 Linked issue

❓ Type of change

• 📖 Documentation (updates to the documentation, readme, or JSdoc annotations)
• 🐞 Bug fix (a non-breaking change that fixes an issue)
• 👌 Enhancement (improving an existing functionality like performance)
• ✨ New feature (a non-breaking change that adds functionality)
• 🧹 Chore (updates to the build process or auxiliary tools and libraries)
• ⚠️ Breaking change (fix or feature that would cause existing functionality to change)

📚 Description

The bcd tests now test console.dir, which causes them to log output as part of the test. This is causing the generated JSON to break and tests to fail, because currently we just naively write the script output to a JSON file. With this PR I've added a shell script that uses sed to strip anything from before a RUNTIME_DATA_START delimiter, menaing that anything printed during the test run itself is ignored.

📝 Checklist

• I have linked an issue or discussion.
• I have updated the documentation accordingly.

[queengooborg]

Good catch, thanks!

Do we perhaps want to have the runner script itself write the file rather than piping logging output to save a step? LGTM though!