Fixes https://github.com/spring-cloud/spring-cloud-stream-samples/issues/163
* Rework a logic for all the Spring Cloud Stream micorservices in the
`testing-demo` into functions without any `@EnableBinding` and friends
* Change test to JUnit 5
* Change the logic in tests to reflect function-based configuration
and modern approaches for testing this kind of applications
* Use `@EmbeddedKafka` instead of rule which is not available in JUnit 5
* Exclude unnecessary auto-configurations from tests
* Decrease `OddEvenSourceTests` time using
`spring.cloud.stream.poller.fixed-delay=1` configuration property
* Removing headerMode from test configuration
1fdbcb1f38