[JAVA] Vector should avoid reallocating validity buffer when necessary

Vector always reallocates validity buffer in the case of all-null or non-null

Ideally we should only allocate if the source was not provided

**Reporter**: [Zhenyuan Zhao](https://issues.apache.org/jira/browse/ARROW-3222) / @zzhao0

_{**Note**: *This issue was originally created as [ARROW-3222](https://issues.apache.org/jira/browse/ARROW-3222). Please see the [migration documentation](https://github.com/apache/arrow/issues/14542) for further details.*}

從 BaseFixedWidthVector.java#L511 和 BitVectorHelper.java#L180 的配置路徑開始，接著追蹤全為 null 的向量和非 null 向量如何處理 validity 緩衝區。當且僅當未提供來源時才進行配置，同時避免不必要的 validity 緩衝區重新配置後，此變更即完成。

由索引模型根據 Issue 內容生成。