support mapping subnet proxy (#978)

- **support mapping subproxy network cidr**
- **add command line option for proxy network mapping**
- **fix Instance leak in tests.

easytier/src/proto/rpc_impl/service_registry.rs

@@ -96,6 +96,10 @@ impl ServiceRegistry {
         self.table.retain(|k, _| k.domain_name != domain_name);
     }
 
+    pub fn unregister_all(&self) {
+        self.table.clear();
+    }
+
     pub async fn call_method(
         &self,
         rpc_desc: RpcDescriptor,