Query streaming progress should publish the result as streaming parts

[ecyshor]

Currently we offer progress sources which contain only the query status and the query result is returned as the materialized value of the source. In certain cases we want the returned body to be streamed in the same source, maybe as a different QueryProgress case class. This is especially imported for queries which return a lot of data as we currently buffer the entire body result in memory by draining the body source when running with progress.