Simplify batch error handling tests #1005
Description
Refactor batch error handling tests in DefaultPulsarConsumerErrorHandlerTests.
- tests are 98% identical (fix that)
- make it more clear the magic numbers expected during verification
Tip
Use the recently added whenBatchRecordListenerOneMessageBatchFailsThenSentToDltProperly as a template and make it re-usable.
Originally motivation in #1002 (comment)