DRILL-2757: Verify operators correctly handle low memory conditions and cancellations
includes:
DRILL-2816: system error does not display the original Exception message
DRILL-2893: ScanBatch throws a NullPointerException instead of returning OUT_OF_MEMORY
DRILL-2894: FixedValueVectors shouldn't set it's data buffer to null when it fails to allocate it
DRILL-2895: AbstractRecordBatch.buildSchema() should properly handle OUT_OF_MEMORY outcome
DRILL-2905: RootExec implementations should properly handle IterOutcome.OUT_OF_MEMORY
DRILL-2920: properly handle OutOfMemoryException
DRILL-2947: AllocationHelper.allocateNew() doesn't have a consistent behavior when it can't allocate
also:
- added UserException.memoryError() with a pre assigned error message
- injection site in ScanBatch and unit test that runs various tpch queries and injects
an exception in the ScanBatch that will cause an OUT_OF_MEMORY outcome to be sent
