GH-3844: Rework messaging annotation with @Bean (#3877)

* GH-3844: Rework messaging annotation with @Bean

Fixes https://github.com/spring-projects/spring-integration/issues/3844

* Make `MessagingAnnotationPostProcessor` as a `BeanDefinitionRegistryPostProcessor`
to process bean definitions as early as possible and register respective messaging
components at that early phase
* Make bean definitions parsing logic optional for AOT and native mode since beans
have bean parsed during AOT building phase
* Introduce a `BeanDefinitionPropertiesMapper` for easier mapping
of the annotation attributes to the target `BeanDefinition`
* Remove `@Bean`-related logic from method parsing process
* Change the logic for `@Bean`-based endpoint bean names:
since we don't deal with methods on the bean definition phase, then method name
does not make sense.
It even may mislead if we `@Bean` name is based on a method by default, so we end up
with duplicated word in the target endpoint bean name.
Now we don't
* Fix `configuration.adoc` respectively for a new endpoint bean name logic
* In the end the new logic in the `AbstractMethodAnnotationPostProcessor`
is similar to XML parsers: we feed annotation attributes to the
`AbstractStandardMessageHandlerFactoryBean` impls

* * Fix language in docs and exception message

src/reference/asciidoc/configuration.adoc

@@ -624,7 +624,7 @@ public class MyFlowConfiguration {
 
     @Bean
     @ServiceActivator(inputChannel = "httpChannel")
-    public MessageHandler httpHandler() {
+    public HttpRequestExecutingMessageHandler httpHandler() {
     HttpRequestExecutingMessageHandler handler = new HttpRequestExecutingMessageHandler("https://foo/service");
         handler.setExpectedResponseType(String.class);
         handler.setOutputChannelName("outputChannel");
@@ -676,12 +676,15 @@ NOTE: The bean names are generated with the following algorithm:
 
 * The `MessageHandler` (`MessageSource`) `@Bean` gets its own standard name from the method name or `name` attribute on the `@Bean`.
 This works as though there were no messaging annotation on the `@Bean` method.
-* The `AbstractEndpoint` bean name is generated with the following pattern: `[configurationComponentName].[methodName].[decapitalizedAnnotationClassShortName]`.
-For example, the `SourcePollingChannelAdapter` endpoint for the `consoleSource()` definition <<annotations_on_beans,shown earlier>> gets a bean name of `myFlowConfiguration.consoleSource.inboundChannelAdapter`.
+* The `AbstractEndpoint` bean name is generated with the following pattern: `[@Bean name].[decapitalizedAnnotationClassShortName]`.
+For example, the `SourcePollingChannelAdapter` endpoint for the `consoleSource()` definition <<annotations_on_beans,shown earlier>> gets a bean name of `consoleSource.inboundChannelAdapter`.
+Unlike with POJO methods, the bean method name is not included in the endpoint bean name.
 See also <<./overview.adoc#endpoint-bean-names,Endpoint Bean Names>>.
+* If `@Bean` cannot be used directly in the target endpoint (not an instance of a `MessageSource`, `AbstractReplyProducingMessageHandler` or `AbstractMessageRouter`), a respective `AbstractStandardMessageHandlerFactoryBean` is registered to delegate to this `@Bean`.
+The bean name for this wrapper is generated with the following pattern: `[@Bean name].[decapitalizedAnnotationClassShortName].[handler (or source)]`.
 
 IMPORTANT: When using these annotations on `@Bean` definitions, the `inputChannel` must reference a declared bean.
-Channels are not automatically declared in this case.
+Channels are automatically declared iif not present in the application context yet.
 
 [NOTE]
 =====