Both xcomposite-egl and xcomposite-glx have rendering issues, and they
do not work with the latest Nvidia driver versions.

These plugins were created to allow testing/debugging of QtWayland-based
compositors on desktops that did not support Wayland natively. At this
time, Wayland is much more widely supported on the desktop, and

[ChangeLog][Extensions][The xcomposite-egl and xcomposite-glx shell
extension protocols are no longer built by default.]

Task-number: QTBUG-92074
Task-number: QTBUG-97985
Pick-to: 6.2
Change-Id: Ifded68b92e91e2d98aa44b8cfc624a4072b30451
Reviewed-by: Liang Qi <liang.qi@qt.io>
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@qt.io>
Reviewed-by: Aleix Pol Gonzalez <aleixpol@kde.org>