Implement withField and dropField for struct types

[andygrove]

Implement withField and dropField for struct types

[dharanad]

take

[Kimahriman]

I believe these are purely used for analysis, and end up just becoming named_struct expressions in the physical plan, so they're probably already supported

[eejbyfeldt]

My understanding is the same as @Kimahriman
that both of these are implemented in terms of UpdateFields which are replaced in the spark Analyzer by the rule ReplaceUpdateFieldsExpression https://github.com/apache/spark/blob/v3.5.2/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/UpdateFields.scala#L79-L87 and based on https://github.com/apache/spark/blob/v3.5.2/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/complexTypeCreator.scala#L746-L757 it looks like it is replace by CreateNamedStruct expression and should therefore be supported.