[cli] add commands for Border Routing counters (#8372)

include/openthread/instance.h

@@ -53,7 +53,7 @@ extern "C" {
  * @note This number versions both OpenThread platform and user APIs.
  *
  */
-#define OPENTHREAD_API_VERSION (260)
+#define OPENTHREAD_API_VERSION (261)
 
 /**
  * @addtogroup api-instance

include/openthread/ip6.h

@@ -885,6 +885,14 @@ typedef struct otBorderRoutingCounters
  */
 const otBorderRoutingCounters *otIp6GetBorderRoutingCounters(otInstance *aInstance);
 
+/**
+ * Resets the Border Routing counters.
+ *
+ * @param[in]  aInstance  A pointer to an OpenThread instance.
+ *
+ */
+void otIp6ResetBorderRoutingCounters(otInstance *aInstance);
+
 /**
  * @}
  *