Add client.rack configuration option to support consumer fetching from closest replica (KIP-392)

**Describe the solution you'd like**

Currently, the `AIOKafkaConsumer` class has no way to set the [`client.rack` consumer config](https://kafka.apache.org/documentation.html#consumerconfigs_client.rack) supported by other clients.
Adding and implementing this option would allow consumers to fetch from the nearest replica.

**Additional context**

More information can be found in [KIP-392](https://cwiki.apache.org/confluence/display/KAFKA/KIP-392%3A+Allow+consumers+to+fetch+from+closest+replica).
This configuration value is [supported by librdkafka](https://github.com/confluentinc/librdkafka/blob/bb2843b5ce32c52954fced9b746205c9340bf96f/CONFIGURATION.md?plain=1#L136) and [confluent-kafka-python](https://github.com/confluentinc/confluent-kafka-python), for example.