The `ConsumerEndpointSpec` extensions for Kotlin don't delegate to the provided `endpointFactoryBean` * Introduce `KotlinConsumerEndpointSpec` extension for `ConsumerEndpointSpec` with the proper delegation to the provided spec * Use `KotlinConsumerEndpointSpec` in the Kotlin-specific `Spec` classes **Cherry-pick to `6.1.x`, `6.0.x` & `5.5.x`**