HPCC-10459 Streamed dataset support for R

Signed-off-by: Richard Chapman <rchapman@hpccsystems.com>
Merge pull request #5528 from richardkchapman/r-stream

HPCC-10459 Streamed dataset support for R

Reviewed-by: Gavin Halliday <ghalliday@hpccsystems.com>