awaitQueueCompletion method
Await for all (including future) submissions using Box.putQueued to be completed (the queue becomes idle for a moment).
Returns true if all submissions were completed or processing was not started; false if shutting down (or an internal error occurred).
Use to wait until all puts by Box.putQueued have finished.
Implementation
bool awaitQueueCompletion() => C.store_await_async_completion(_ptr);