Add support for dynamic destinations when writing to Kafka

BEAM-5798 introduced support to write to multiple topics when writing to Kafka.
This is similar in function to what DynamicDestinations do on BigQueryIO, AvroIO and TextIO but with a different API. The goal of this issue is to add the dynamic destinations style API to KafkaIO API e.g. KafkaIO.write().to(new DynamicDestination(...)).