Transforming Hive simple UDF (using JAR) expression may incur CNFE in later evaluation

In SPARK-26560, we ensured that Hive UDF using JAR is executed regardless of current thread context classloader.

cloud_fan pointed out another potential issue in post-review of SPARK-26560 - quoting the comment:

Found a potential problem: here we call HiveSimpleUDF.dateType (which is a lazy val), to force to load the class with the corrected class loader.

However, if the expression gets transformed later, which copies HiveSimpleUDF, then calling HiveSimpleUDF.dataType will re-trigger the class loading, and at that time there is no guarantee that the corrected classloader is used.

I think we should materialize the loaded class in HiveSimpleUDF.

This JIRA issue is to track the effort of verifying the potential issue and fixing the issue.