Simplify batch error handling tests

[onobc]

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)