HPCC-10022 Option to generate a persist for each unique ECL hash

Signed-off-by: Gavin Halliday <gavin.halliday@lexisnexis.com>
Merge pull request #4914 from ghalliday/issue10022

HPCC-10022 Option to generate a persist for each unique ECL hash

Reviewed-By: Richard Chapman <rchapman@hpcsystems.com>