The current `KafkaBootstrapConfiguration` provides a couple beans
which can be overridden in the target project, but at the same time
the latest Spring Boot is going to fail with the
`BeanDefinitionOverrideException`

* Change `KafkaBootstrapConfiguration` to be as an
`ImportBeanDefinitionRegistrar` instead of `@Configuration`
* Check for bean definition existence before registering
`KafkaListenerAnnotationBeanPostProcessor` and `KafkaListenerEndpointRegistry`
in this `KafkaBootstrapConfiguration`
* Deffer such a bean definition processing with the
`KafkaListenerConfigurationSelector`