Allow Embedded Code to Access Local Dataset Partitions

It would be very useful to access the local partitions of a dataset from within EMBEDs that have been flagged as distributed. Currently when a dataset is passed into an EMBED marked distributed the entire dataset is coalesced and then passed into the embedded code.

This request is similar to: https://track.hpccsystems.com/browse/HPCC-13559 which was marked as resolved. However, the resolving ticket https://track.hpccsystems.com/browse/HPCC-13534 & PR does not allow local/distributed access to datasets from within embedded code.

An example of what I would like to be able to do:

doWrite(streamed dataset ds, const varstring name) := EMBED(C++ : distributed,local?)