feat: adds option to mongoose to ensure indexes (#9155)

Adds option `ensureIndexes` to Mongoose adapter, which will ensure
indexes are ready prior to completing connection.

test/generateDatabaseAdapter.ts

@@ -10,6 +10,7 @@ export const allDatabaseAdapters = {
   import { mongooseAdapter } from '@payloadcms/db-mongodb'
 
   export const databaseAdapter = mongooseAdapter({
+    ensureIndexes: true,
     url:
       process.env.MONGODB_MEMORY_SERVER_URI ||
       process.env.DATABASE_URI ||