xwayland: Create duplicate TrueColor GLXFBConfigs for Composite

Similar to what is done in Xorg. Not doing this prevented apps from
using GLX with a Composite visual, e.g. Firefox WebRender or Chromium.

v2:
* Fix inverted direct_color test, fixes Chromium as well.
* Drop Composite extension guards, since other Xwayland code calls
  compRedirectWindow/compUnredirectWindow unconditionally anyway.

Closes: xorg/xserver#921
Fixes: 84692415 "xwayland: Add EGL-backed GLX provider"
Reviewed-by: Adam Jackson <ajax@redhat.com> # v1
3 jobs for xwayland-glx-duplicate-configs-for-composite in 6 minutes and 55 seconds (queued for 1 second)
Status Name Job ID Coverage
  Docker Image
passed debian-testing #1199280

00:00:32

 
  Build And Test
passed autotools-build-and-test #1199281

00:06:23

passed meson-build-and-test #1199282

00:02:27