HPCC-10655 DISTRIBUTION may core on eclagent if input record is small

Using the wrong rowAllocator to create distribution accumulator

Signed-off-by: Richard Chapman <rchapman@hpccsystems.com>
HPCC-10580 Implement DISTRIBUTION in roxie

Signed-off-by: Richard Chapman <rchapman@hpccsystems.com>
Merge pull request #5275 from richardkchapman/roxie-distribution

Roxie distribution

Reviewed-by: Gavin Halliday <ghalliday@hpccsystems.com>