We want to be able to keep all sdk's up-to-date, and having a script to do that is our first try.
While we could parse C++ code to generate C# code, I feel it's cleaner to have a C api.

For a happy path, creating an extension, we need a C api for configfile.h, extension.h and resource.h.
The biggest task is creating the resource C api.

Design doc: https://docs.google.com/document/d/1xITgxkLeBTOy5yP7rmqvrTcabe_iZrIJ_cW2DXTRcFo/edit?usp=sharing
Subtask of #8063