Don't write the referenced segment IDs in the segment buffer

The work done for OAK-4844 restores the capability of a Segment to efficiently maintain a list of referenced segment IDs. The referenced segment IDs are marshalled to the underlying buffer by the SegmentBufferWriter and unmarshalled by the current Segment as needed. While this solution works, it would be beneficial to encapsulate this concern in a separate set of classes, especially when considering future development directions (e.g. OAK-4582).