ScreenAlignedUVs does not handle opengl space properly

ScreenAlignedUVs does not handle OpenGL space properly. There are differences in Metal and OpenGL window coordinates, so it works correctly for iOS and not for OpenGL.

1. Post process material looks like this:
   • [Link Removed]
2. Run attached project on iOS
3. Observe results like this:
   • [Link Removed]
4. Run attached project on xperia (or similar device)
5. Observe results like this:
   • [Link Removed]
6. Google Pixel showed even worse results