introduce uptime monitor for easytier public nodes (#1250)

easytier/src/instance_manager.rs

@@ -134,6 +134,12 @@ impl NetworkInstanceManager {
         Ok(ret)
     }
 
+    pub fn get_network_info(&self, instance_id: &uuid::Uuid) -> Option<NetworkInstanceRunningInfo> {
+        self.instance_map
+            .get(instance_id)
+            .and_then(|instance| instance.value().get_running_info())
+    }
+
     pub fn list_network_instance_ids(&self) -> Vec<uuid::Uuid> {
         self.instance_map.iter().map(|item| *item.key()).collect()
     }