[BUG]fastjson由1.83升级至2.0.52版本，instance of不生效

```
public void findAll(JSONObject jsonObject, String findKey, Set includeSourceSet) {
for (String key : jsonObject.keySet()) {
Object value = jsonObject.get(key);
if (value instanceof JSONObject) {
findAll((JSONObject) value, findKey, includeSourceSet);
} else if (value instanceof JSONArray) {
JSONArray jsonArray = (JSONArray) value;
for (int i = 0; i < jsonArray.size(); i++) {
findAll(jsonArray.getJSONObject(i), findKey, includeSourceSet);
}
} else if (key.equals(findKey)) {
includeSourceSet.add(value.toString());
}
}
}
```

Start by reproducing the reported behavior from the code snippet with fastjson2 2.0.52 and compare it with version 1.83. Trace the runtime types returned by jsonObject.get(key), especially JSONObject and JSONArray values, then add a focused regression test. Done means the intended instanceof branches work consistently and the test passes.

Written by the indexing model from the issue text.