[BUG] 字符串转json对象，无法输出期待结果

### 问题描述
*简要描述您碰到的问题。*

### 环境信息
*请填写以下信息：*

- OS信息： win10
- JDK信息：JDK17
- 版本信息：Fastjson2 2.0.x43

### 重现步骤
String testStr = "{en:{\"SAVE\":\"save\",\"EMAIL\":\"E-MAIL\"}}";
JSONObject jsonObject = new JSONObject();
jsonObject.put("Il8N_SCRIPT", testStr);
System.out.println(jsonObject);
输出结果：{"Il8N_SCRIPT":"{en:{\"SAVE\":\"save\",\"EMAIL\":\"E-MAIL\"}}"}
```

### 期待的正确结果
期望输出结果：{"Il8N_SCRIPT":{"en":{"SAVE":"save","EMAIL":"E-MAIL"}}}

请问我该如何做才能输出期望结果？

Reproduce the issue with the supplied Java snippet, then inspect the JSONObject.put call and the related JSON parsing or serialization behavior. Done should establish whether the reported nested-object output is supported and, if so, produce the expected JSON; otherwise, clarify the required usage or documented limitation.

Written by the indexing model from the issue text.