Add support for $setWindowFields aggregation stage.

Add a SetWindowFieldsOperation to the aggregation framework.

The builder API allows fluent declaration of the aggregation stage as shown in the sample below.

SetWindowFieldsOperation.builder()
	.partitionByField("state")
	.sortBy(Sort.by(Direction.ASC, "date"))
	.output(AccumulatorOperators.valueOf("qty").sum())
	.within(Windows.documents().fromUnbounded().toCurrent().build())
	.as("cumulativeQuantityForState")
	.build();

Closes #3711
Original pull request: #3739.

Author: christophstrobl