bfc6931329
Fixes https://github.com/spring-projects/spring-integration/issues/3869 * Move `ContextHolderRequestHandlerAdvice` to the `core` module for more general purposes * Add `ContextHolderRequestHandlerAdviceTests` * Rework `DelegatingSessionFactoryTests` to rely on the `ContextHolderRequestHandlerAdvice`. This allows us to remove unnecessary XML configuration for this test class * Document the feature