Comprehensive query and read results sample

Write a sample showing
1) Use the insert+poll overload of InsertJob to start a query expecting a lot of data returned
2) use `.then` on the future returned from step 1 to invoke a callback to read the results of the finished query
3) the callback should use multiple threads to read the query results in parallel, each thread reading from its own ReadStream

Start by locating the InsertJob insert+poll overload, the future returned from it, and the ReadStream API. Build the sample around the listed sequence, with the callback reading query results in parallel through separate ReadStream instances; completion is a working comprehensive query-and-read-results sample.

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