HPCC-11382 - Add SuperHashTableOf::next

Signed-off-by: Jake Smith <jake.smith@lexisnexis.com>
Merge pull request #5835 from jakesmith/hpcc-11382

HPCC-11382 - Add SuperHashTableOf::next

Reviewed-by: Gavin Halliday <ghalliday@hpccsystems.com>