feat: automatically enable duplex to stream request body

[pi0]

🔗 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

This PR enables to support of stream request bodies (ReadableStream and Readable) out of the box by setting (semi standard?!) duplex: 'half' option.

Limitations:

• This feature is only supported with native node fetch (Node.js 18+)
• For some reason, i couldn't enable "transformed-encoding": "chunked" and was causing the unsupported error. Therefore in tests, an explicit content-length is set (which i guess ideally we should not need)

📝 Checklist

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