DRILL-519: Fix regression with decorrelation in tpch21 (based on updated fix for correlation bug in Optiq, allow PushFilterThroughJoin to be applied to JoinRelBase.)
DRILL-1077: OperationStats enhancements —

Add setLongStat and setDoubleStat to set metrics directly.
Remove shared HashTableMetrics class
Add ResizeTime for hash aggregate and hash join.
Not all RootExec should report the metrics in SenderStats. Break up into RootExec specific MetricDefs.
Add BYTES_SENT metric for all RootExec
Rename N_SENDERS to N_RECEIVERS
DRILL-1078: Added metrics to unordered receiver (+ renaming) and merging receiver.
DRILL-561: Implement btrim/trim

Make use of existing UTF8 function

Added test for btrim
DRILL-841: Using BigDecimal to round and truncate.
Add debug info.
WIP.  Fix hash distribution exchange.