[Java] Make sure Netty Allocator has correct behavior with empty ArrowBuf

Include a test which ensures that the Netty Allocator returns an empty-behaving byte buffer when users allocate a zero byte buffer

**Reporter**: [Ji Liu](https://issues.apache.org/jira/browse/ARROW-8870) / @tianchen92

_{**Note**: *This issue was originally created as [ARROW-8870](https://issues.apache.org/jira/browse/ARROW-8870). Please see the [migration documentation](https://github.com/apache/arrow/issues/14542) for further details.*}

Start by locating the Netty allocator and its handling of zero-byte ArrowBuf allocations. Add the requested regression test for allocating a zero-byte buffer and verify that the returned byte buffer behaves as empty. The issue does not name a source or test file, so repository search is needed first.

Written by the indexing model from the issue text.