Deduplicate Switch/If expressions according to the intended use case (#98)
Deduplicate Switch/If expressions according to the intended use case (#98)

* Rename Switch/If expressions to reflect their use case better

Also use `Literal` in case value to restrict according to the use case

* Use Literal for SwitchExpression if field
substrait-io/substrait,substrait-io/substrait,substrait-io/substrait,substrait-io/substrait