* GH-2690: Add MessageHandlerMethodFactory beans
Fixes https://github.com/spring-projects/spring-integration/issues/2690
For more end-user flexibility and for simplicity of the `MessagingMethodInvokerHelper`
logic, add `IntegrationContextUtils.MESSAGE_HANDLER_FACTORY_BEAN_NAME` and
`IntegrationContextUtils.LIST_MESSAGE_HANDLER_FACTORY_BEAN_NAME`
infrastructure beans
* Use mentioned beans in the `MessagingMethodInvokerHelper` if any,
otherwise fallback to the locally configured `MessageHandlerMethodFactory`,
although this is necessary only for our non-Spring-based unit tests
* Relax `BeanFactory` requirement for the `EvaluationContext` since it
is going to be there in the Spring-based environment, but might not be
available in the plain unit tests
* Provide some optimization and refactoring for the `MessagingMethodInvokerHelper`
* Remove deprecated `HandlerMethodArgumentResolversHolder` and
`ARGUMENT_RESOLVERS_BEAN_NAME` & `LIST_ARGUMENT_RESOLVERS_BEAN_NAME`
bean definitions and constants for their names
* * Revert `getEvaluationContext(false)` usage.
* Fix `MessagingMethodInvokerHelper` to propagate `BeanFactory` to
argument resolvers if any
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