[FEATURE]考虑增加一个JSON.toJSONString(bean, context, Feature)函数

### 请描述您的需求或者改进建议
context作为全局配置，后面的feature只是作为单次的配置，譬如有时候需要对json进行格式化，就可以这样使用
JSON.toJSONString(bean, context, JSONWriter.Feature.PrettyFormat);

### 请描述你建议的实现方案
略

### 描述您考虑过的替代方案
略

#### 附加信息
略

Start by inspecting the existing JSON.toJSONString overloads and JSONWriter.Feature handling. Add the requested overload accepting a bean, context, and feature, then verify that a per-call feature such as PrettyFormat works while the context remains the global configuration; add or update tests for this behavior.

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