Remove dependency on X11 as we can do everything with EGL already

In 2019 we added support for Wayland and with it came a proper extension for querying the driver options: EGL_MESA_query_driver This is more than 3 years already, so I feel confident enough to drop the old Xlib code and rely solely on the EGL code path.

This MR will remove all references and dependencies on X11, thus making us free to only use the EGL extension. This change shouldn't break anything as long as users are running a version of mesa that is newer than 2019.