DM: add DM parameter for command monitor

Libvirt or kata container needs to send some commands
(such as VM destory command) to the DM instance of User VM
through command monitor socket, they will specify the socket
path and pass this path name to DM instance through DM parameter.

In this patch, add new DM parameter (cmd_monitor) to get socket
path from libvirt or kata container. If cmd_monitor is specified,
it initialize and deinitialize command monitor in DM main loop.

v2-->v3:
	Include command monitor initialization and deinitialization.

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

@@ -7,4 +7,5 @@
 
 int init_cmd_monitor(struct vmctx *ctx);
 void deinit_cmd_monitor(void);
+int acrn_parse_cmd_monitor(char *arg);
 #endif