Allow modules to have private and public include directories

[ikskuh]

Follow-up from #18160:

After reading the source i've seen that modules now have a include_dirs property which is neat. But what i've figured is that some modules will require private and public include directories.

The private ones are required to build the C source code of the modules, but the public ones are required for using the module, so it would be useful to be able to either make them available to all other modules, or just to the ones depending on it