Related to https://stackoverflow.com/questions/72851234/error-in-startup-application-when-using-serviceactivator-in-spring-cloud-stream
The `MessagingAnnotationPostProcessor` register an `endpoint` bean for Messaging Annotation on POJO methods.
The `IntegrationMBeanExporter` post-process such a bean and registers respective MBean.
It does this not in optimal way scanning all the `IntegrationConsumer` beans for requested `MessageHandler`
which may cause a `BeanCurrentlyInCreationException`.
* Rework the logic of the `IntegrationMBeanExporter.postProcessAbstractEndpoint()` to propagate provided endpoint
for the monitor registration to bypass application context scanning for matched name.
* Swap `equals()` for `monitor` since an `extractTarget()` may return `null`
* Some other code clean in the `IntegrationMBeanExporter`
* Change one of the `@ServiceActivator` in the configuration for the `ScatterGatherHandlerIntegrationTests`
to POJO method.
However, this didn't fail for me with original code unlike in the sample application provided in the mentioned SO thread.
**Cherry-pick to `main`**
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