MXS-1929: Make core ResultSet functions private

The functions in the core that generate a ResultSet are now private.

server/core/internal/modules.hh

@@ -0,0 +1,24 @@
+#pragma once
+/*
+ * Copyright (c) 2016 MariaDB Corporation Ab
+ *
+ * Use of this software is governed by the Business Source License included
+ * in the LICENSE.TXT file and at www.mariadb.com/bsl11.
+ *
+ * Change Date: 2022-01-01
+ *
+ * On the date above, in accordance with the Business Source License, use
+ * of this software will be governed by version 2 or later of the General
+ * Public License.
+ */
+
+#include "modules.h"
+
+#include <maxscale/resultset.hh>
+
+/**
+ * @brief Return a resultset that has the current set of modules in it
+ *
+ * @return A Result set
+ */
+ResultSet *moduleGetList();