The build scripts are still referring to gpu tests as being opengl.
Although they can also use Metal or Vulkan. This PR only replaces
the work `opengl` with `gpu` for build options.
Special note is that the windows argument `with_opengl_tests` is
also replaced with `with_gpu_tests` for consistency.
Pull Request: https://projects.blender.org/blender/blender/pulls/116030