DATAREDIS-337 - Improve handling of overridden methods in MessageListenerAdapter.

Previously overriding message handler methods of the delegate passed to MessageListenerAdapter resulted in the message handler method called multiple times. We now make sure that a message handler method is only found and invoked  once.
Maybe it would make sense to extend the `MethodFilter` below to find the most specific method.
Thinking of something like [UniqueMethodFilter](https://github.com/spring-projects/spring-integration/blob/2baea786b1e608df4093fc52bb270e65e9fbc719/spring-integration-core/src/main/java/org/springframework/integration/util/UniqueMethodFilter.java#L38).