findAsync Cursor return should include _id

[RobMayer]

Describe the bug

db.findAsyc and db.findOneAsync Cursor return type does not include _id

Expected behavior If you're fetching a record or a list of records, that list of records should probably include the _id in its types return types of insert or update include them.

[tex0l]

I changed the type of Cursor so that it extends Promise<Document<T>> like its method execAsync instead of Promise<T>, as Cursor is a sort of "thenable" as it reimplements manually then, catch and finally simply by making a call to execAsync followed by then, catch or finally.

[tex0l]

It landed in 4.0.4