Kafka Streams function detection improvements (#1033)

* Kafka Streams function detection improvements

Allow Kafka Streams functions defined as Component beans
to be candidates for establishing bindings. Currently, Kafka Streams
functions need to be written as functional beans using @Bean.
Adding this improvement so that if applications prefer to write
the business logic using @Component, then it is possible to do so.

Adding test cases to verify the behavior.

Resolves https://github.com/spring-cloud/spring-cloud-stream-binder-kafka/issues/1030

* Kafka Streams functions and bean name overriding

Whn Kafka Streams function bean names are overridden,
there is an issue with scanning it properly for binding.
Addressing this issue.

* Adding docs for Component based model

* Addressing PR review comments

docs/src/main/asciidoc/kafka-streams.adoc

@@ -77,6 +77,22 @@ NOTE: If the destination property is not set on the binding, a topic is created
 
 Once built as a uber-jar (e.g., `kstream-consumer-app.jar`), you can run the above example like the following.
 
+If the applications choose to define the functional beans using Spring's `Component` annotation, the binder also suppports that model.
+The above functional bean could be rewritten as below.
+
+```
+@Component(name = "process")
+public class SimpleConsumer implements java.util.function.Consumer<KStream<Object, String>> {
+
+    @Override
+    public void accept(KStream<Object, String> input) {
+        input.foreach((key, value) -> {
+            System.out.println("Key: " + key + " Value: " + value);
+        });
+    }
+}
+```
+
 [source]
 ----
 java -jar kstream-consumer-app.jar --spring.cloud.stream.bindings.process-in-0.destination=my-topic