add change stream notifications for more DDL operations

Original Summary

mongodb create/delete index should trigger change stream

Original Description

I've already posted a question on [stack overflow|https://stackoverflow.com/questions/60368424/mongodb-create-delete-index-wont-trigger-change-stream] but no response.

Why change stream can't receive DDL events like create/delete index, applyOps, convertToCapped, and so on? I think it's important for users that using change-stream to receive all the change events from MongoDB, not only DML but also DDL.