With ISPN-13434 we now have access to segment information much easier when iterating as well as nice guarantees to retrievals and segment completion being on the same thread and not concurrent. We need to improve include current state to use these benefits.

1. Track notified keys by segment and clear them out as a segment completes to reduce memory overhead
2. Ensure that all queues are cleaned up when a segment completes as soon as possible
3. Remove extraneous code around segment completion and additional entry creations