router: add to service options; add dns and static implementations (#1733)

* config/cmd: add router to service options

* router/service: use micro client

registry.go

@@ -0,0 +1,8 @@
+package registry
+
+import "github.com/micro/go-micro/v2/router"
+
+// NewRouter returns an initialised registry router
+func NewRouter(opts ...router.Option) router.Router {
+	return router.NewRouter(opts...)
+}