[Java] Provide writeNull interface from ListWriter

**Reporter**: [Thippana Vamsi Kalyan](https://issues.apache.org/jira/browse/ARROW-8686) / @tvamsikalyan

_{**Note**: *This issue was originally created as [ARROW-8686](https://issues.apache.org/jira/browse/ARROW-8686). Please see the [migration documentation](https://github.com/apache/arrow/issues/14542) for further details.*}

Start by locating ListWriter and reviewing its existing writer interfaces and null-handling methods. The issue provides no file or test names, so confirm the intended API and expected behavior with the linked ARROW-8686 context; done means ListWriter exposes the requested writeNull interface with coverage for its behavior.

Written by the indexing model from the issue text.