Improve dictionary filter evaluating notEq

When evaluating `notEq`, if the column may contain nulls and the `notEq` value is non-null, the row-group must not be skipped. In such scenario reading dictionary and compare values is not necessary.

**Reporter**: [Yujiang Zhong](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=zhongyuj) / @zhongyujiang

_{**Note**: *This issue was originally created as [PARQUET-2245](https://issues.apache.org/jira/browse/PARQUET-2245). Please see the [migration documentation](https://issues.apache.org/jira/browse/PARQUET-2502) for further details.*}

该 issue 未指出源文件、测试或入口点。首先定位字典过滤器的实现及其测试，然后复现列可能包含 null 的 notEq 情况，并确认不会在进行不必要的字典比较的情况下跳过 row group。

由索引模型根据 Issue 内容生成。