fix: Fix router middleware detection in Express instrumentation

So it's not immune to function name changes which maybe introduced in bundling or other tools instrumentation process

Author: medikoo

node/packages/sdk/lib/instrumentation/express/instrument-layer-prototype.js

@@ -40,7 +40,7 @@ module.exports.install = (layerPrototype) => {
       }
       expressRouteData = expressSpansMap.get(req);
       const { routeSpan, openedSpans } = expressRouteData;
-      const isRouterMiddleware = !routeSpan && this.name === 'bound dispatch';
+      const isRouterMiddleware = Boolean(!routeSpan && this.route);
       const middlewareSpanName = (() => {
         if (routeSpan) {
           return `express.middleware.route.${[
@@ -77,7 +77,9 @@ module.exports.install = (layerPrototype) => {
           if (!middlewareSpan.endTime) {
             expressRouteData.openedSpans.delete(middlewareSpan);
             middlewareSpan.close();
-            if (this.name === 'bound dispatch') delete expressRouteData.routeSpan;
+            if (this.route) {
+              delete expressRouteData.routeSpan;
+            }
           }
         } catch (error) {
           reportError(error);