nodeparser: Print debug message before child

This puts the message up top, where it can be seen,
and not at the other end of an endless tree of children.

Update tests to match.

gsk/gskrendernodeparser.c

@@ -2767,13 +2767,13 @@ render_node_print (Printer       *p,
 
         start_node (p, "debug");
 
-        append_node_param (p, "child", gsk_debug_node_get_child (node));
         /* TODO: We potentially need to escape certain characters in the message */
         if (message)
           {
             _indent (p);
             g_string_append_printf (p->str, "message: \"%s\";\n", message);
           }
+        append_node_param (p, "child", gsk_debug_node_get_child (node));
 
         end_node (p);
       }

testsuite/gsk/nodeparser/debug.node

@@ -1,5 +1,5 @@
 debug {
+  message: "I'm a debug node.";
   child: container {
   }
-  message: "I'm a debug node.";
 }