JIRA: https://jira.spring.io/browse/INT-4539
The `IntegrationFlowBeanPostProcessor` doesn't check for prototype beans
and just override them in the application context with the singletons
* Since we can't in the DSL understand if provided object is a prototype
or not, we try to check for its bean definition by possible bean name.
Use `NamedComponent` for possible bean name to check.
* Remove `final` from the `IntegrationComponentSpec.get()` since its
result is not visible for CGI proxies when it is declared as a `@Bean`
and subsequent `getObject()` produces a new internal object
* Verify prototype beans with new test in the `IntegrationFlowTests`
**Cherry-pick to 5.0.x**
c4d6cf2b50