What is the problem the feature request solves?

I would ike to refactor the serde logic for Cast so that it is more consistent with how we implement serde for other expressions.

We now have an IncompatExpr trait for tagging expressions that are incompatible with Spark. CometCast has an isSupported method that returns Compatible, Incompatible, or Unsupported. I would like to try and unify these approaches.

Describe the potential solution

No response

Additional context

No response