perf: simplify method signatures and reduce clone across multiple files (#1663)

easytier/src/instance/virtual_nic.rs

@@ -366,7 +366,7 @@ impl VirtualNic {
         Ok(())
     }
 
-    async fn create_tun(&mut self) -> Result<tun::platform::Device, Error> {
+    async fn create_tun(&self) -> Result<tun::platform::Device, Error> {
         let mut config = Configuration::default();
         config.layer(Layer::L3);