DM: add new monitor module

This monitor module is to initialize socket intance, register
handlers to handle command from socket message, close socket,
free socket instance:
init_cmd_monitor: initialize socket intance and register handlers
to handle command.
deinit_cmd_monitor: close socket and free socket instance.

In this patch DM makefile is updated to build command monitor.

v1--v2:
	Update socket path and update log message format.
	Parse JSON format command message using libcjson lib APIs.
v2-->v3:
	Use socket path length MACRO.
	Update JSON format command message to {"command": "xxx"}.

Tracked-On: #5921

Signed-off-by: Xiangyang Wu <xiangyang.wu@intel.com>
Acked-by: Wang, Yu1 <yu1.wang@intel.com>

devicemodel/include/cmd_monitor.h

@@ -0,0 +1,10 @@
+/*
+ * Copyright (C) 2022 Intel Corporation
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+#ifndef _CMD_MONITOR_H_
+#define _CMD_MONITOR_H_
+
+int init_cmd_monitor(struct vmctx *ctx);
+void deinit_cmd_monitor(void);
+#endif