[BUG] com.alibaba:fastjson:2.0.62 lombok + null/isNull 字段 序列化与旧版本一致,但反序列化失败, 不兼容

### 问题描述
*简要描述您碰到的问题。*

```xml

com.alibaba
fastjson
1.2.83

```
升级到
```xml

com.alibaba
fastjson
2.0.62

```

com.alibaba.fastjson.support.spring.GenericFastJsonRedisSerializer 反序列化预期不一致

### 环境信息
*请填写以下信息：*

- OS信息： [e.g.：macOS tahoe 26.3.1(a) M5 32 GB]
- JDK信息： [e.g.：Amazon Corretto 17.0.17]
- 版本信息：[e.g.：Fastjson2 2.0.62]

### 重现步骤
*如何操作可以重现该问题：*

```java

import com.alibaba.fastjson.support.spring.GenericFastJsonRedisSerializer;
import lombok.Data;
import lombok.ToString;
import org.junit.jupiter.api.Assertions;
import org.junit.jupiter.api.Test;

import java.util.concurrent.atomic.AtomicReference;

class FastjsonCompatibilityTest {

@Test
void parseError() {

String location = GenericFastJsonRedisSerializer.class.getProtectionDomain()
.getCodeSource()
.getLocation().getPath();

int lastSep = location.lastIndexOf('/');

String fastjsonVersion = location.substring(lastSep + 1);
System.out.println("Fastjson version: " + fastjsonVersion);

boolean isFastjson2 = fastjsonVersion.startsWith("fastjson-2");

doTest(LombokFieldNameNull.class, isFastjson2);
doTest(LombokFieldNameIsNull.class, isFastjson2);
doTest(LombokFieldNameNotNull.class, false);

doTest(FieldNameNullNoGet.class, false);
doTest(FieldNameIsNullNoGet.class, false);
doTest(FieldNameNotNullNoGet.class, false);

doTest(FieldNameNullGet.class, isFastjson2);
doTest(FieldNameNullSet.class, false);

}

void doTest(Class cls, boolean expectedExceptionOn2ButOkOn1) {
GenericFastJsonRedisSerializer genericFastJsonRedisSerializer = new GenericFastJsonRedisSerializer();

Object obj = null;
try {
obj = cls.getDeclaredConstructor().newInstance();
} catch (Exception e) {
throw new RuntimeException(e);
}

byte[] jsonBytes = genericFastJsonRedisSerializer.serialize(obj);
System.out.println("JSONSTR" + new String(jsonBytes));

AtomicReference deserializeObj = new AtomicReference<>();

if (expectedExceptionOn2ButOkOn1) {
Assertions.assertThrows(Exception.class, () -> {
deserializeObj.set(genericFastJsonRedisSerializer.deserialize(jsonBytes));
System.out.println("DESERIALIZED OBJ: " + deserializeObj.get());
});
} else {
deserializeObj.set(genericFastJsonRedisSerializer.deserialize(jsonBytes));
System.out.println("DESERIALIZED OBJ: " + deserializeObj.get());
org.assertj.core.api.Assertions.assertThat(deserializeObj.get())
.usingRecursiveComparison()
.isEqualTo(obj);
}

}
}

@Data
class LombokFieldNameNull {
boolean Null;
}

@Data
class LombokFieldNameIsNull {
boolean isNull;
}

@Data
class LombokFieldNameNotNull {
boolean nul;
}

@ToString
class FieldNameNullNoGet {
boolean Null;
}

@ToString
class FieldNameIsNullNoGet {
boolean isNull;
}

@ToString
class FieldNameNotNullNoGet {
boolean nul;
}

@ToString
class FieldNameNullGet {
boolean Null;

public boolean isNull() {
return Null;
}
}

@ToString
class FieldNameNullSet {
boolean Null;

public void setNull(boolean Null) {
this.Null = Null;
}
}
```
切换1.2.83到2.0.62, 变量isFastjson2的表现会不一致

### 期待的正确结果
*对您期望发生的结果进行清晰简洁的描述。*
com.alibaba:fastjson:2.0.62能真正兼容com.alibaba:fastjson:1.2.83

### 相关日志输出
*请复制并粘贴任何相关的日志输出。*

#### 附加信息
*如果你还有其他需要提供的信息，可以在这里填写（可以提供截图、视频等）。*

Start by running the supplied FastjsonCompatibilityTest with fastjson 1.2.83 and 2.0.62, focusing on GenericFastJsonRedisSerializer and the LombokFieldNameNull, LombokFieldNameIsNull, and FieldNameNullGet cases. Compare the serialized output and deserialization results; done means fastjson 2.0.62 deserializes these cases compatibly with 1.2.83 without breaking the existing passing cases.

Written by the indexing model from the issue text.