add db.collection.getInfo() collection method

We already have db.getCollectionInfos(). However, numerous users have run into issues where they aren't able to get information specific to a collection (information such as what listCollections provides) because they do not have the necessary privileges to do so.

Exposing a new method on the collection, one that returns the same information as db.getCollectionInfos() - but for the current namespace - will address most of these issues.