GPU: Add GLSL preprocessor

This splits the GLSL processing into its own file
as it will grow in complexity.

Removes the complexity from `datatoc` and chain them
during the build process.

Rel #128076

Pull Request: https://projects.blender.org/blender/blender/pulls/128261

intern/opensubdiv/CMakeLists.txt

@@ -85,10 +85,9 @@ if(WITH_OPENSUBDIV)
     add_definitions(-D_USE_MATH_DEFINES)
   endif()
 
-  data_to_c_simple(
+  glsl_to_c(
     internal/evaluator/shaders/glsl_compute_kernel.glsl
     SRC
-    STRIP_LEADING_C_COMMENTS
   )
 else()
   list(APPEND SRC