message: testbed can now use the standard addon loading logic
diff: import * as express from "express";
  import * as bodyParser from "body-parser";
  import { IModelDb } from "@build/imodeljs-core/lib/backend/IModelDb";
  -import { NodeAddonRegistry, NodeAddonPackageName } from "@build/imodeljs-core/lib/backend/NodeAddonRegistry";
  +import { NodeAddonRegistry } from "@build/imodeljs-core/lib/backend/NodeAddonRegistry";
  import { TestbedConfig, TestbedIpcMessage } from "../common/TestbedConfig";
  import { TestGatewayImpl } from "./TestGatewayImpl";
  @@ -27,8 +27,7 @@ TestGatewayImpl.register();
  TestbedConfig.initializeGatewayConfig();
  // tslint:disable-next-line:no-var-requires
  -const addon = require(NodeAddonPackageName.computeDefaultImodelNodeAddonName());
  -NodeAddonRegistry.registerAddon(addon);
  +NodeAddonRegistry.loadAndRegisterStandardAddon();
  const app = express();
  app.use(bodyParser.text());
  