Create MaxNode/MinNode implementing UpdateLeafNode. Ensure we can parse $max/$min to a MaxNode/MinNode.
- depends on
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                    SERVER-28621 Parse BSON update expression into an UpdateNode tree -         
- Closed
 
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- is depended on by
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                    SERVER-28777 Always parse update expression as an UpdateNode tree when featureCompatibilityVersion=3.6 -         
- Closed
 
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