Batch Retrieve in as_complete

[ncollier]

as_complete can be slow over remote queues - each individual result is returned from the remote. A batch argument would improve performance by allowing the remote to retrieve a batch of batch_size and return that amount. This is particularly useful when the ME is synchronous and waiting for all results, or asynchronous but working with a large number of results.

[ncollier]

local implementation can accumulate values in list and yield from that list. Remote function should accumulate and return that list to the queue implementation which then yields from that list.

[ncollier]

Implemented here: d90e5d0