[Bug]: Add a Python Kafka read test that uses the with_metadata option

[chamikaramj]

What happened?

Python Kafka with_metadata option [1] uses a transform in Java side [2] that is not invoked by regular Python KafkaIO tests. So we need a separate test for this.

[1] https://github.com/apache/beam/blob/d578e3df7c963e57f251fb27739fbc1d3811e722/sdks/python/apache_beam/io/kafka.py#L162

[2] https://github.com/apache/beam/blob/d578e3df7c963e57f251fb27739fbc1d3811e722/sdks/java/io/kafka/src/main/java/org/apache/beam/sdk/io/kafka/KafkaIO.java#L1781

Issue Priority

Priority: 2

Issue Component

Component: io-py-kafka

[chamikaramj]

cc: @johnjcasey

[brucearctor]

I think since added by @chamikaramj , @johnjcasey was tagged, has io, kafka, p2 and bug labels, this has been 'triaged' therefore removing the 'awaiting triage' label... Someone do advise if I misunderstand how we want to handle triaging [ ex: does someone need to be assigned ?]