HPCC-10861 Include XmlSchema in JSON formatted WsWorkunits::WUResult

Signed-off-by: Anthony Fishbeck <anthony.fishbeck@lexisnexis.com>
Merge pull request #5430 from afishbeck/jsonResultWithXmlSchema

HPCC-10861 Include XmlSchema in JSON formatted WsWorkunits::WUResult

Reviewed-By: Gordon Smith <gordon.smith@lexisnexis.com>
Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>