Fix support for Wireframe and parametric nodes by resolving
compilation failures surrounding barycentric coordinates.
A final missing part of the Metal implementation for barycentric
coordinates was missing.
Feedback also addressed to move barycentric calculation out
of code-gen and into surface_lib.
Authored by Apple: Michael Parkin-White
This also resolves#103606.
Ref #96261
Pull Request: https://projects.blender.org/blender/blender/pulls/105740
96c6349cbf