wayland: Initialize in a single step

Before we first created the MetaWaylandCompositor instance, which would
repare Clutter/Cogl so they could initialize and turn on Wayland display
server features, then later to initialize the rest. Now that part is
done by the Wayland infrastructure itself, so we don't need the early
initialization. Simplify things a bit by centralizing it all into a
single meta_wayland_compositor_new() call.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1861>

src/core/meta-context.c

@@ -317,10 +317,6 @@ meta_context_setup (MetaContext  *context,
 
   init_introspection (context);
 
-#ifdef HAVE_WAYLAND
-  priv->wayland_compositor = meta_wayland_compositor_new (context);
-#endif
-
   return META_CONTEXT_GET_CLASS (context)->setup (context, error);
 }
 
@@ -335,7 +331,7 @@ meta_context_start (MetaContext  *context,
 #ifdef HAVE_WAYLAND
   if (meta_context_get_compositor_type (context) ==
       META_COMPOSITOR_TYPE_WAYLAND)
-    meta_wayland_compositor_setup (priv->wayland_compositor);
+    priv->wayland_compositor = meta_wayland_compositor_new (context);
 #endif
 
   priv->display = meta_display_new (context, error);