Change HashAggregationOperator to support multi channel group by
Isolate aggregates in separate classloader
Change join operator to support multi channel hash
Remove unused packIfNecessary from visitSemiJoin
Change sort, topN and window operators to support multiple channels

Remove single channel packing from LocalExecutionPlanner
Change variance intermediates to use hand built slice instead of a multi channel tuple
Change TupleInfo to support only a single value
Remove unused DirectFieldOrderedTupleComparator
Remove getTypes, getFieldCount, and getFieldOffset from TupleInfo
Remove unused UncompressedBlockCursor
Remove unused AlternatingNullsBlockCursor
Remove unused sequence cursors
Remove tuple field read and write methods
Remove field from Input
Replace Tuple toValues method with getObjectValue
Add stats to ExpressionCompiler
Fix thread safety issue in LocalQueryRunner
Listen for buffer closure
Schedule splits in batches
Add simple PerfTest runner