Emit OpenCL C types, not host types, in JSON header

It was agreed that opencl c types are more appropriate for the library
API uses, and that the JSON header in the CLI driver should be
consistent with that.
WebCLHeader: remove WebCLTypes dependency

The only thing left after dropping host type mapping was using
supportedBuiltinTypes, which can be replaced in one more readable line
here
Remove WebCLConfiguration dependency from WebCLHeader

This requires copypasting two constants and one expression but is worth
it as WebCLHeader can now be moved to the driver executable
Expose found kernels in WebCLValidator API
Move WebCLHeader to the driver executable

Still using the temporary C++ API, up next creating a C API and only
using that