HPCC-9272 Add implicit CHOOSEN to filtered-index-read[n]

Signed-off-by: Gavin Halliday <gavin.halliday@lexisnexis.com>
Merge pull request #5067 from ghalliday/issue9272

HPCC-9272 Add implicit CHOOSEN to filtered-index-read[n]

Reviewed-By: Jamie Noss <james.noss@lexisnexis.com>
Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>