Note that this ticket should only handle non-removable position-based windows, as the execution state for such windows already exists for accumulators (AccumulatorState). So the task here is to walk the parsed tree and produce the correct AccumulatorState along with the corresponding window manager to be used by the aggregation stage.

The full list of supported accumulators: sum, avg, stddev, min, max, count, first, last, push, addToSet