Docs: Add docs and useful info for debugging CODAL, including with MakeCode & MicroPython

Flags to enable for debug prints, how to enable those flags in MakeCode and MicroPython builds, etc.

We were considering having this information in the MakeCode and MicroPython documentation as well, but ultimately this is usually necessary when debugging from the CODAL layer, so this would be a good place to have them. And it'd be more efficient to have this in a repo like this one, rather than trying to find the "right place" (which might not exists yet) in MakeCode/MicroPython docs.

Start by surveying the repository's existing CODAL documentation and the build documentation for MakeCode and MicroPython. Document the debug-print flags and how to enable them in each build, keeping the guidance in the CODAL documentation; done when a newcomer can follow the steps to debug from the CODAL layer.

Written by the indexing model from the issue text.