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

### 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

Start with the with_metadata option in sdks/python/apache_beam/io/kafka.py and the related transform in sdks/java/io/kafka/src/main/java/org/apache/beam/sdk/io/kafka/KafkaIO.java. Read the existing Python KafkaIO tests and add a separate Kafka read test that invokes with_metadata. Done means the Python test exercises the Java-side transform that regular KafkaIO tests miss.

Written by the indexing model from the issue text.