[FEATURE] 支持将单值解析为数组

### 请描述您的需求或者改进建议
```java
final JSONObject object = JSON.parseObject("{\"a\":1,\"b\":\"b\"}");
System.out.println(object.getJSONArray("a"));
System.out.println(object.getJSONArray("b"));
```
当前返回如下
```java
null

com.alibaba.fastjson2.JSONException: offset 1, character b, line 1, column 2, fastjson-version 2.0.39 b
at com.alibaba.fastjson2.reader.ObjectReaderImplList.readObject(ObjectReaderImplList.java:576)
at com.alibaba.fastjson2.JSONObject.getJSONArray(JSONObject.java:219)

```

### 请描述你建议的实现方案
期望能正确将1 和 字符串b解析为对应的数组格式

### 描述您考虑过的替代方案
fastjson1 支持上述的使用方式

#### 附加信息
当前使用的版本：
```xml

com.alibaba.fastjson2
fastjson2
2.0.39

```

Start with JSONObject.getJSONArray and trace the failing path into ObjectReaderImplList.readObject, using the issue's numeric and string examples as the reproduction. Confirm the behavior against fastjson 1 if available, then add coverage showing that scalar values are converted to the expected array forms and that the relevant tests pass.

Written by the indexing model from the issue text.