context: Add entry points for context configuration

Configuration is the first step of the lifetime of a context, after
creation; it's here where argc/argv is processed, and it's determined
what kind of compositor, etc, it is going to be.

The tests always run as Wayand compositors, so the configuration is
quite simple, but will involve more steps later on.

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

src/core/meta-context.c

@@ -22,6 +22,8 @@
 
 #include "core/meta-context-private.h"
 
+#include "core/util-private.h"
+
 enum
 {
   PROP_0,
@@ -40,6 +42,37 @@ typedef struct _MetaContextPrivate
 
 G_DEFINE_TYPE_WITH_PRIVATE (MetaContext, meta_context, G_TYPE_OBJECT)
 
+static MetaCompositorType
+meta_context_get_compositor_type (MetaContext *context)
+{
+  return META_CONTEXT_GET_CLASS (context)->get_compositor_type (context);
+}
+
+gboolean
+meta_context_configure (MetaContext   *context,
+                        int           *argc,
+                        char        ***argv,
+                        GError       **error)
+{
+  MetaCompositorType compositor_type;
+
+  if (!META_CONTEXT_GET_CLASS (context)->configure (context, argc, argv, error))
+    return FALSE;
+
+  compositor_type = meta_context_get_compositor_type (context);
+  switch (compositor_type)
+    {
+    case META_COMPOSITOR_TYPE_WAYLAND:
+      meta_set_is_wayland_compositor (TRUE);
+      break;
+    case META_COMPOSITOR_TYPE_X11:
+      meta_set_is_wayland_compositor (FALSE);
+      break;
+    }
+
+  return TRUE;
+}
+
 static void
 meta_context_get_property (GObject    *object,
                            guint       prop_id,