Add qianfan free model "ERNIE-Speed-128K" (#1253)

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## Change
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Add qianfan free model "ERNIE-Speed-128K" and complete the test call
1.add qianfan free model `ERNIE_SPEED_128K("ERNIE-Speed-128K",
"completions"),`
in class dev.langchain4j.model.qianfan.QianfanChatModelNameEnum . and
complete the test call
2.update exception description in
dev.langchain4j.model.qianfan.QianfanStreamingChatModel `(or there is no
model definition in the QianfanChatModelNameEnum class)`

## General checklist
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[X] -->
- [x] There are no breaking changes
- [ ] I have added unit and integration tests for my change
- [x] I have manually run all the unit and integration tests in the
module I have added/changed, and they are all green
- [ ] I have manually run all the unit and integration tests in the
[core](https://github.com/langchain4j/langchain4j/tree/main/langchain4j-core)
and
[main](https://github.com/langchain4j/langchain4j/tree/main/langchain4j)
modules, and they are all green
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until the PR is reviewed and approved. -->
- [ ] I have added/updated the
[documentation](https://github.com/langchain4j/langchain4j/tree/main/docs/docs)
- [ ] I have added an example in the [examples
repo](https://github.com/langchain4j/langchain4j-examples) (only for
"big" features)

Co-authored-by: songjinming <songjinming@jd.com>

langchain4j-qianfan/src/main/java/dev/langchain4j/model/qianfan/QianfanChatModelNameEnum.java

@@ -9,6 +9,7 @@ public enum QianfanChatModelNameEnum {
     ERNIE_BOT_4("ERNIE-Bot 4.0", "completions_pro"),
     ERNIE_BOT_8("ERNIE-Bot-8K", "ernie_bot_8k"),
     ERNIE_BOT_TURBO("ERNIE-Bot-turbo", "eb-instant"),
+    ERNIE_SPEED_128K("ERNIE-Speed-128K", "completions"),
     EB_TURBO_APPBUILDER("EB-turbo-AppBuilder", "ai_apaas"),
     YI_34B_CHAT("Yi-34B-Chat", "yi_34b_chat"),
     BLOOMZ_7B("BLOOMZ-7B","bloomz_7b1"),

langchain4j-qianfan/src/main/java/dev/langchain4j/model/qianfan/QianfanStreamingChatModel.java

@@ -65,7 +65,7 @@ public class QianfanStreamingChatModel implements StreamingChatLanguageModel  {
         this.endpoint=Utils.isNullOrBlank(endpoint)? QianfanChatModelNameEnum.getEndpoint(modelName):endpoint;
 
         if (Utils.isNullOrBlank(this.endpoint)) {
-            throw new IllegalArgumentException("Qianfan is no such model name. You can see model name here: https://cloud.baidu.com/doc/WENXINWORKSHOP/s/Nlks5zkzu");
+            throw new IllegalArgumentException("Qianfan is no such model name(or there is no model definition in the QianfanChatModelNameEnum class). You can see model name here: https://cloud.baidu.com/doc/WENXINWORKSHOP/s/Nlks5zkzu");
         }
 
         this.baseUrl = getOrDefault(baseUrl,  "https://aip.baidubce.com");