Controlling Visibility

[JohnLCaron]

See https://zsmb.co/mastering-api-visibility-in-kotlin

So we have

1. public
2. public but allowing use of InternalLibraryApi with @file:OptIn(InternalLibraryApi::class)
3. public but marked as @InternalLibraryApi
4. internal
5. private

We want to keep things as low down as possible.

But:

• Some tests require access to some classes marked @InternalLibraryApi. This requires OptIn (even though it would have worked if the class was internal).
• Hdf4Clib, Hdf5Clib and NetcdfClib all require access to the cdm builders.

openNetchdfFile(filename, NetchdfFileFormat.HDF4) fas been added to replace direct calls to Netcdf3File, Hdf5File, Hdf4File.

[JohnLCaron]

Since the native API will need to be separate due to memory management, we can probably not worry about visibility.