[FirebaseServerApp] add a new serverapp type for usage tracking. (#8094)

Add a new serverapp string so that register version to track FirebaseServerApp usage.

packages/app/src/firebaseServerApp.ts

@@ -21,10 +21,11 @@ import {
   FirebaseServerAppSettings,
   FirebaseOptions
 } from './public-types';
-import { deleteApp } from './api';
+import { deleteApp, registerVersion } from './api';
 import { ComponentContainer } from '@firebase/component';
 import { FirebaseAppImpl } from './firebaseApp';
 import { ERROR_FACTORY, AppError } from './errors';
+import { name as packageName, version } from '../package.json';
 
 export class FirebaseServerAppImpl
   extends FirebaseAppImpl
@@ -77,6 +78,8 @@ export class FirebaseServerAppImpl
     // will never trigger.
     this._serverConfig.releaseOnDeref = undefined;
     serverConfig.releaseOnDeref = undefined;
+
+    registerVersion(packageName, version, 'serverapp');
   }
 
   get refCount(): number {