HPCC-11922 Changes from code review

- IXmlWriterExt.rewindTo() not valid for flusher type
- Move wsexcept from LN/esp/esdllib to esp/services/common
- Move non json specific logic from JsonHelpers to HttpParamHelpers
- Cleared tmp strbuffer upon every appendjsonexceptions iteration
- Moved buildJsonMsg from ws_ecl to JsonHelpers
- ws_ecl now utilizes JsonHelpers

Signed-off-by: rpastrana <rodrigo.pastrana@lexisnexis.com>
HPCC-11922 Changes from code review

- Substitute all static method class for namespace scoping
- Refactor odd member field nomenclature

Signed-off-by: rpastrana <rodrigo.pastrana@lexisnexis.com>
HPCC-11922 More changes from code review

- Refactor member vars

Signed-off-by: rpastrana <rodrigo.pastrana@lexisnexis.com>