KIP-456 — Helper classes to make it simpler to write test logic with TopologyTestDriver

Discarded Kafka 2.4 StreamsTesting

Proposes `TestInputTopic` and `TestOutputTopic` helper classes for `TopologyTestDriver` to simplify test record production and consumption (discarded in favor of KIP-470 which superseded it). Without typed topic wrappers, every `TopologyTestDriver` test requires constructing `ConsumerRecordFactory` objects and passing deserializers on each `readOutput` call, producing test boilerplate that dwarfs the application logic.

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