* Register `BeanDefinition`s for DSL components.
That way we get a gain when the `BeanDefinition` is involved,
e.g. Spring Cloud Function uses this approach to determine the generics
of the target `Function` class
* This programmatic `BeanDefinition` registration approach
(available since SF-5.0) allows us to avoid some manual lifecycle processes:
bean initialization, autowiring, event listener registration etc.
* Rework `IntegrationFlowContext` to register and remove `BeanDefinition`s as well
* Remove unused `registerComponents` flag from the `StandardIntegrationFlow`.
With the proper logic in the `IntegrationFlowContext` it does not make sense any more
* Remove redundant `AnnotationGatewayProxyFactoryBean` in the `IntegrationFlows`;
populate `defaultRequestChannel` directly to the `GatewayProxyFactoryBean` instance
* Add an overloaded `IntegrationFlows.from(Class, String)` to allow to specify an
explicit bean name for the target gateway proxy
* Extract and populate bean name from the `@MessagingGateway.name()` in the
`AnnotationGatewayProxyFactoryBean`
* Stop lifecycles in the `AmqpTests` after using for proper test suit shutdown
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