[core-gl-kit] Create metapackage like `xorg-x11` that includes `xorg-drivers`

On `mark-testing`, `x11-base/xorg-x11` is installed on my system in the `world` set, but `emerge -c` wants to remove `x11-base/xorg-drivers`. That's clearly not the right thing to do, because it will also remove `x11-drivers/xf86-input-evdev` and friends, rendering my Xserver inoperable... won't it? Did something change in how these packages are implemented?

I suspect it's a dependency issue, but haven't checked the ebuild so perhaps I'm wrong about the source of this problem.

Inspect the x11-base/xorg-x11 and x11-base/xorg-drivers ebuilds first, focusing on the dependency relationship described in the issue. Reproduce the behavior with emerge -c and verify that the completed dependency fix keeps xorg-drivers and its xf86-input-evdev dependencies from being removed.

Written by the indexing model from the issue text.