xwayland: Disable the XTEST extension by default

Most features from the XTEST extension cannot work on Wayland, which can
be misleading for applications which would (optionally) rely on that
extension to implement some features.

Disable the XTEST extension by default to make it clear that XTEST is
not supposed to work on Xwayland, so that X11 clients are not tempted to
use it.

Using the standard command line option "+extension XTEST" can re-enable
it at runtime, if really needed.

Signed-off-by: Olivier Fourdan <ofourdan@redhat.com>
Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>
Acked-by: Karol Herbst <karolherbst@gmail.com>
4 jobs for disable-xtest-on-xwayland in 4 minutes and 35 seconds (queued for 1 second)
latest
Status Job ID Name Coverage
  Docker Image
passed #3454470
debian-testing

00:00:22

 
  Build And Test
passed #3454471
autotools

00:04:13

passed #3454472
meson

00:01:24

passed #3454473
meson-noglamor

00:00:43