WireGuard inbound: Reply fake pong to ICMP ping (#6855)

https://github.com/XTLS/Xray-core/pull/6015#issuecomment-4321525342

proxy/wireguard/server.go

@@ -134,6 +134,7 @@ func NewServer(ctx context.Context, conf *DeviceConfig) (*Server, error) {
 	}
 	// Install the stack's protocol handlers before the device can deliver packets to it (Start -> dev.Up).
 	CreateForwarder(stack, s.HandleConnection)
+	CreateICMPEchoResponder(stack)
 	return s, nil
 }