Put the fields saved by glPush/PopAttrib into the sub-structure declared
as Attrib. This will make glPush/PopAttrib much faster because it will
only save and restore that structure.
Acked-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6946>