XD-2098: Add KafkaMessageBus

Needs some more polish, but this is finally passing all tests
That said, why are you even setting `PARTITION_HEADER` ? - it's not used by this bus (it's used in `buildPartitionRoutingExpression`) which is not invoked from this bus.

Also, it's not clear why the bus supports the bus-level partitioning properties, when the partitioning is done by Kafka itself...

`SUPPORTED_PRODUCER_PROPERTIES` should not include `PRODUCER_PARTITIONING_PROPERTIES`.