Session change streams currently don't expose a type that implements Stream the way that session cursors do; ideally they'd have a mirroring interface.

The lack of current implementation is an artifact of the Rust lifetime system:

• wrapping a session cursor stream means iteration in the stream cannot update the underlying session cursor as the stream has an exclusive borrow
• avoiding that by giving an encapsulated future an exclusive borrow prevents state like the resume token from being visible during that borrow
• shifting the state to being reference-counted would require holding that reference across a poll resume point, requiring unsafe code