This adds support for the extension and always
set the clip state value to 0..1 to align with vulkan
and metal. Moreover this is needed for the Reverse Z
implementation.
Note that this is a OpenGL 4.5 feature and is not
required to start Blender. So there must still be
a fallback path for now.
Rel #138898
Pull Request: https://projects.blender.org/blender/blender/pulls/138941
8ac5940e33