This change makes it possible for platforms to only support high quality
normal rendering. This is part of {T82856} where current AMD drivers
running on the polaris architecture does not support the low quality
setting due to a driver bug.
In a next commit the work around will be enabled.
This wraps the functionality used to speedup EEVEE volumetrics.
This touches the rendering code of EEVEE as it should fix a mis-usage of
the GL barrier. The barrier changed type and location, removing an
unused barrier.
