[Java] Add hasNull flag to Vectors

Add has null flag to Arrow Vector so that for vectors without any null, the null check process should be skipped.

**Reporter**: [Yurui Zhou](https://issues.apache.org/jira/browse/ARROW-5198) / @yuruiz
#### PRs and other links:
- [GitHub Pull Request apache/arrow#4199](https://github.com/apache/arrow/pull/4199)

_{**Note**: *This issue was originally created as [ARROW-5198](https://issues.apache.org/jira/browse/ARROW-5198). Please see the [migration documentation](https://github.com/apache/arrow/issues/14542) for further details.*}

该 issue 涉及 Arrow Vectors，并链接到 pull request apache/arrow#4199；首先审查该 pull request 以及它所修改的 Java vector 实现。在其中确认预期的 has-null 行为和完成状态；完成意味着没有 null 的 vector 会跳过 null 检查过程。

由索引模型根据 Issue 内容生成。