Allow $stdDevPop & stdDevSamp operators to be used in $project, $addFields, $set, ... aggregation stages.

[christophstrobl]

Starting with MongoDB 5.0 $stdDevPop & stdDevSamp operators can be used in more stages than just $group.

Full list available via:

https://docs.mongodb.com/manual/reference/operator/aggregation/stdDevPop/
https://docs.mongodb.com/manual/reference/operator/aggregation/stdDevSamp/

[mp911de]

Should work already as we accept and(AggregationExpression expression) in ProjectionOperation.