GH-9561: Make DelayedMessageWrapper JSON-serializable

Fixes: #9561
PR: https://github.com/spring-projects/spring-integration/pull/9561

The `DelayHandler.DelayedMessageWrapper` cannot be deserialized when using `RedisMessageStore` and JSON serialization:
```
org.springframework.data.redis.serializer.SerializationException: Could not read JSON:Cannot construct instance of `org.springframework.integration.handler.DelayHandler$DelayedMessageWrapper` (no Creators, like default constructor, exist): cannot deserialize from Object value (no delegate- or property-based Creator)
 at [Source: UNKNOWN; byte offset: #UNKNOWN]
	at org.springframework.data.redis.serializer.GenericJackson2JsonRedisSerializer.deserialize(GenericJackson2JsonRedisSerializer.java:311)
```

* More code clean up and refactoring in the test

(cherry picked from commit 73bb813b53)

spring-integration-core/src/main/java/org/springframework/integration/handler/DelayHandler.java

@@ -31,6 +31,8 @@ import java.util.concurrent.locks.Lock;
 import java.util.concurrent.locks.ReentrantLock;
 import java.util.stream.Stream;
 
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonProperty;
 import org.aopalliance.aop.Advice;
 
 import org.springframework.aop.framework.ProxyFactory;
@@ -97,6 +99,7 @@ import org.springframework.util.ObjectUtils;
  * @author Artem Bilan
  * @author Gary Russell
  * @author Christian Tzolov
+ * @author Youbin Wu
  *
  * @since 1.0.3
  */
@@ -688,7 +691,10 @@ public class DelayHandler extends AbstractReplyProducingMessageHandler implement
 
 		private final Message<?> original;
 
-		DelayedMessageWrapper(Message<?> original, long requestDate) {
+		@JsonCreator(mode = JsonCreator.Mode.PROPERTIES)
+		DelayedMessageWrapper(@JsonProperty("original") Message<?> original,
+				@JsonProperty("requestDate") long requestDate) {
+
 			this.original = original;
 			this.requestDate = requestDate;
 		}

spring-integration-core/src/main/java/org/springframework/integration/support/json/JacksonJsonUtils.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2022 the original author or authors.
+ * Copyright 2002-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -46,6 +46,7 @@ import org.springframework.messaging.support.GenericMessage;
  *
  * @author Artem Bilan
  * @author Gary Russell
+ * @author Youbin Wu
  *
  * @since 3.0
  *
@@ -63,7 +64,8 @@ public final class JacksonJsonUtils {
 					"org.springframework.integration.support",
 					"org.springframework.integration.message",
 					"org.springframework.integration.store",
-					"org.springframework.integration.history"
+					"org.springframework.integration.history",
+					"org.springframework.integration.handler"
 			);
 
 	private JacksonJsonUtils() {