v6 hole punch (#873)

Some devices have ipv6 but don't allow input connection, this patch add hole punching for these devices.

- **add v6 hole punch msg to udp tunnel**
- **send hole punch packet when do ipv6 direct connect**

easytier/src/common/stun.rs

@@ -890,7 +890,7 @@ impl StunInfoCollectorTrait for MockStunInfoCollector {
             last_update_time: std::time::Instant::now().elapsed().as_secs() as i64,
             min_port: 100,
             max_port: 200,
-            public_ip: vec!["127.0.0.1".to_string()],
+            public_ip: vec!["127.0.0.1".to_string(), "::1".to_string()],
         }
     }