DRILL-6080: Sort incorrectly limits batch size to 65535 records
closes #1090
* Sort incorrectly limits batch size to 65535 records rather than 65536.
* This PR also includes a few code cleanup items.
* Fix for overflow in offset vector in row set writer
* Performance tool update
* Replace "unsafe" methods with "set" methods
* Also fixes an indexing issue with nullable writers
* Removed debug & timing code
* Increase strictness for batch size
