BIT_PACKING is written by default when Definition or Repetition levels are empty

As discussed in https://github.com/apache/arrow/discussions/47113 , this package is writing the deprecated BIT_PACKING encoding to the column metadata and the DataPageHeader. This is only seems to happens when rep/def levels are empty. I think this is where it's happening:

```java
public class DevNullValuesWriter extends ValuesWriter {
....
public Encoding getEncoding() {
return BIT_PACKED;
}
}
```

Wouldn't it make sense to just return RLE?

I've seen this in parquet-java 1.15.1 and Overture Maps files using 1.13.1.

首先定位 DevNullValuesWriter 并检查其 getEncoding() 实现，然后跟踪该值如何传递到列元数据和 DataPageHeader。确认空的重复级别和定义级别不再生成已弃用的 BIT_PACKED 编码，而是使用 RLE。

由索引模型根据 Issue 内容生成。