General Changes

• Parallelize startup of table scan task splits.
• Fixed index join driver resource leak.
• Improve memory accounting for JOINs and GROUP BYs.
• Improve CPU efficiency of coordinator.
• Added Asia/Chita, Asia/Srednekolymsk, and Pacific/Bougainville time zones.
• Fix task leak caused by race condition in stage state machine.
• Fix blocking in Hive split source.
• Free resources sooner for queries that finish prematurely.