Enhance Transactional Producer Exception Handling

In general, KafkaProducer could throw both fatal and non-fatal errors as KafkaException, which makes the exception catching hard. Furthermore, not every single fatal exception (checked) is marked on the function signature yet as of 2.7.

We should have a general supporting strategy in long term for this matter, as whether to declare all non-fatal exceptions as wrapped KafkaException while extracting all fatal ones, or just add a flag to KafkaException indicating fatal or not, to maintain binary compatibility.