Add tests of `KafkaProducer` for various Acks levels

[jeffwidman]

It looks like there's not tests of the new KafkaProducer for the various acks levels: https://github.com/dpkp/kafka-python/blob/master/test/test_producer.py

These tests are present for the old/deprecated producers here: https://github.com/dpkp/kafka-python/blob/3ff3d75004f94fd55fa089297d3e2376e33ccda7/test/test_producer_integration.py#L417-L466

We should add/migrate tests of these scenarios to the new KafkaProducer.

Reason: We just observed a very confusing scenario in production where a KafkaProducer-based producer is sending thousands of messages using acks=1, none of which returned any errors. However, two messages are missing when we dump all messages from that topic. So I just want to make sure this part of kafka-python has test coverage to eliminate it from potential root causes.