HPCC-10368 regress should give more information on syntax

Improve built-in help and usage hints.

Signed-off-by: Attila Vamos <attila.vamos@gmail.com>
Merge pull request #5110 from AttilaVamos/HPCC-10368-fix2

HPCC-10368 regress should give more information on syntax

Reviewed-by: Gavin Halliday <ghalliday@hpccsystems.com>