HPCC-12290 Reimplement jarray using templates

Signed-off-by: Gavin Halliday <gavin.halliday@lexisnexis.com>
Related because the elements in the array are now Owned<IHqlExpressions> not IInterface * *.

It might be if all the arrays are changed and we keep the existing structure then they would be Owned<IInterfaces> instead.