Removing unused SegPref from AMS.
Refactored implementation of preferenced allocation policy from VM arena to general purpose arena.
Eliminating SegPrefExpress in most places, especially where there wasn’t really any preference.
Eliminating special case knowledge about garbage collection from the arena.
Adding arena extension back to the arena allocation policy.
Deleting a chunk’s address range from the arena’s freeCBS when the chunk is destroyed.  Otherwise, the memory gets allocated and an assertion fires when that memory is not in any chunk.