ClangFormat: apply to source, most of intern

Apply clang format as proposed in T53211.

For details on usage and instructions for migrating branches
without conflicts, see:

https://wiki.blender.org/wiki/Tools/ClangFormat

source/blender/gpu/shaders/gpu_shader_image_frag.glsl

@@ -6,5 +6,5 @@ uniform sampler2D image;
 
 void main()
 {
-	fragColor = texture(image, texCoord_interp);
+  fragColor = texture(image, texCoord_interp);
 }