INT-3521 `completions` for ChannelInterceptorList

JIRA: https://jira.spring.io/browse/INT-3521
Let's avoid this object creation if not necessary; something like...

````
        @Override
        public Message<?> receive() {
-               Deque<ChannelInterceptor> interceptorStack = new ArrayDeque<ChannelInterceptor>();
+               Deque<ChannelInterceptor> interceptorStack = null;
                try {
-                       if (!this.getInterceptors().preReceive(this, interceptorStack)) {
+                       ChannelInterceptorList interceptors = this.getInterceptors();
+                       if (interceptors.size() > 0) {
+                               interceptorStack = new ArrayDeque<ChannelInterceptor>();
+                       }
+                       if (!interceptors.preReceive(this, interceptorStack)) {
                                 return null;
                         }
````

and only invoke `afterReceiveCompletion` if not null.