[client] Refactor/iface pkg (#2646)

Refactor the flat code structure

client/iface/configurer/uapi.go

@@ -0,0 +1,26 @@
+//go:build !windows
+
+package configurer
+
+import (
+	"net"
+
+	log "github.com/sirupsen/logrus"
+	"golang.zx2c4.com/wireguard/ipc"
+)
+
+func openUAPI(deviceName string) (net.Listener, error) {
+	uapiSock, err := ipc.UAPIOpen(deviceName)
+	if err != nil {
+		log.Errorf("failed to open uapi socket: %v", err)
+		return nil, err
+	}
+
+	listener, err := ipc.UAPIListen(deviceName, uapiSock)
+	if err != nil {
+		log.Errorf("failed to listen on uapi socket: %v", err)
+		return nil, err
+	}
+
+	return listener, nil
+}