JIRA: https://jira.spring.io/browse/INT-3521 INT-3521: Rework invocation `index` to the `Deque` of invoked interceptors Conflicts: src/reference/docbook/whats-new.xml INT-3521: Address PR comments Create an `interceptorStack` only if there are `interceptor` on the channel. Invoke `afterSend(Receive)Completion` only `if (interceptorStack != null)` Minor Doc Polishing