This PR introduces support for the extension `VK_KHR_fragment_shader_barycentric`,
and includes a few miscellaneous improvements related to it.
1. Add support for `VK_KHR_fragment_shader_barycentric`, if the physical device
supports it. Otherwise, gpu_BaryCoord is generated through an injected geom
shader, like it was previously.
2. Simplify the logic of checking has_geometry_stage in vert shader.
3. Fix a potential issue of location mismatch in an injected geom shader.
Related to #127687Resolves#126228
Pull Request: https://projects.blender.org/blender/blender/pulls/127995
9f4da19800