main: Initialize Wayland just before MetaDisplay

Wayland support is not really a "backend" thing, it just lacked a better
place to store its instance pointer. Eventually we'll have a better
place, but prepare for that by initializing it together with the more
similar subsystems.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1833>

src/core/main.c

@@ -852,6 +852,11 @@ meta_start (void)
 {
   meta_prefs_init ();
 
+#ifdef HAVE_WAYLAND
+  if (meta_is_wayland_compositor ())
+    meta_backend_init_wayland (meta_get_backend ());
+#endif
+
   if (!meta_display_open ())
     meta_exit (META_EXIT_ERROR);
 }