DRILL-7436: Fix record count, vector structure issues in several operators
Adds additional vector checks to the BatchValidator.
Enables checking for the following operators:
* FilterRecordBatch
* PartitionLimitRecordBatch
* UnnestRecordBatch
* HashAggBatch
* RemovingRecordBatch
Fixes vector count issues for each of these.
Fixes empty-batch (record count = 0) handling in several of the
above operators. Added a method to VectorContainer to correctly
create an empty batch. (An empty batch, counter-intuitively,
needs vectors allocated to hold the 0 value in the first
position of each offset vector.)
Disables verbose logging for MongoDB tests. Details are written to
the log rather than the console.
Disables two invalid Mongo tests. See DRILL-7428.
Adjusts the expression tree materializer to not add the LATE type
to Union vectors. (See DRILL-7435.)
Ensures that Union vectors contain valid vectors for each subtype.
The present fix is a work-around, see DRILL-7434 for a better
long-term fix.
Cleans up code formatting and other minor issues in each file touched
during the fixes in this PR.
