remove lastEmittedDocPerShard logic from QueryThenFetchTask

was always null / unused
forbid using ``alter table add column`` on a single partition.
support functions in QueryThenFetchTask

removes LocalMerge with TopN projection from qtf-plans
remove PlannerFunctionArgumentCopier

became unused with fe468cf64b6407fd1b2e06d90927fb3322923dd4
correctly handle empty clustered by values or values containing commas

as elasticsearch misinteprets empty string or strings containing commas
do not use these as routing for requests