[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.*}

此 issue 涉及 Arrow Vectors，並連結到 pull request apache/arrow#4199；請先檢視該 pull request 以及它所修改的 Java vector 實作。在其中確認預期的 has-null 行為與完成狀態；完成表示沒有 null 的 vector 會跳過 null 檢查程序。

由索引模型根據 Issue 內容生成。