fix(graph): serializer add builtin support for spring ai Message. (#2275)

* Serializer add builtin support for spring ai Message.

* optimize serializer implementation

* code format

* register fallback handler

Author: chickenlj

spring-ai-alibaba-graph-core/src/main/java/com/alibaba/cloud/ai/graph/agent/ReactAgent.java

@@ -39,6 +39,7 @@
 import org.apache.commons.collections4.CollectionUtils;
 
 import com.alibaba.cloud.ai.graph.state.strategy.ReplaceStrategy;
+
 import org.springframework.ai.chat.client.ChatClient;
 import org.springframework.ai.chat.messages.AssistantMessage;
 import org.springframework.ai.chat.messages.Message;