[lvthanh03]

Switches the lightweight deletions producer and the querylog producer from confluent_kafka.Producer to arroyo's KafkaProducer.

• KafkaProducer polls in its own thread, so the lw deletions flush_producers thread and the poll(0) calls are removed
• delivery callbacks are attached to the returned future
• metrics and warning logs are unchanged
• state.flush_producer() (only called at shutdown by the subscriptions executors) now also closes the producer

Refs STREAM-1929

[linear-code]

STREAM-1929