Add support for $replaceOne & $replaceAll aggregation operators

[christophstrobl]

The $replaceOne and $replaceAll operators should be supported via the StringOperatorFactory.

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See:

• https://docs.mongodb.com/v5.0/reference/operator/aggregation/replaceOne/
• https://docs.mongodb.com/v5.0/reference/operator/aggregation/replaceAll/