python-ecosys/debugpy: Add comprehensive VS Code testing guide.

Adds detailed step-by-step instructions for testing the MicroPython debugpy
implementation with Visual Studio Code, including:

- Prerequisites and setup requirements
- VS Code launch configurations for debugging
- Basic and advanced test applications
- Complete testing procedures and expected results
- Troubleshooting guide and known limitations

The guide provides everything needed to validate that the debugpy port works
correctly with VS Code's debugging interface.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: pi-anl