DRILL-2932: Fix: Error reported via System.out rather than exception message
Main:
- Removed the System.out.println(...) from submissionFailed(...).
- Put UserException's message text in SQLException's message (didn't just wrap).
- Added undoing of extra wrapping by AvaticaStatement.execute...(...).
- Created unit test for execute...(...) exceptions.
- Refined related exception handling (handled cases separately, narrowed
throws declarations and catches).
JDBC cleanup:
- Renamed ex -> executionFailureException
- Added getNext() method doc. comment.
- Removed some obsolete alignment spaces.
Added "review this" TODOs re DRILL-2933 (probably-obsolete SchemaChangeException):
- DrillCursor;
- MergingRecordBatch, ParquetResultListener, PrintingResultsListener, QueryWrapper, RecordBatchLoader, UnorderedReceiverBatch;
- TestDrillbitResilience, TestTextColumn, BaseTestQuery, DrillTestWrapper.
