Wait for any of the supplied Asyncs to complete. If the first
to complete throws an exception, then that exception is re-thrown by
waitAny. The input list must be non-empty.
If multiple Asyncs complete or have completed, then the value
returned corresponds to the first completed Async in the list.
Wait for any of the supplied asynchronous operations to complete. The
value returned is a pair of the Async that completed, and the
result that would be returned by wait on that Async. The
input list must be non-empty.
If multiple Asyncs complete or have completed, then the value
returned corresponds to the first completed Async in the list.