[Java] Add accessors to get type parameters from vector classes

Vector classes contain private copies of each param in the `ArrowType`, but does not have any public api to access them. So if given a vector you would have to get the `Field` from the and cast to the correct type. For example, with a `TimeStampMicroTZVector` and trying to get the timezone:

```

if field.getType.isInstanceOf[ArrowType.Timestamp] &&
field.getType.asInstanceOf[ArrowType.Timestamp].getTimezone
```

It would be more convenient to have direct accessors for these type params for the vector types that have parameters:

- DecimalVector
- FixedSizeBinaryVector
- ListVector
- TimeStamps with timezones
- FixedSizedListVector
- Unions

**Reporter**: [Bryan Cutler](https://issues.apache.org/jira/browse/ARROW-1361) / @BryanCutler
#### PRs and other links:
- [GitHub Pull Request apache/arrow#972](https://github.com/apache/arrow/pull/972)

_{**Note**: *This issue was originally created as [ARROW-1361](https://issues.apache.org/jira/browse/ARROW-1361). Please see the [migration documentation](https://github.com/apache/arrow/issues/14542) for further details.*}

まず、issue で名前が挙げられているベクトルクラスと、リンクされた pull request apache/arrow#972 を確認してください。これらの private な ArrowType パラメーターがどのように表現されているかを確認し、その後、DecimalVector、FixedSizeBinaryVector、ListVector、タイムゾーン対応の timestamp ベクトル、FixedSizeListVector、および union に直接アクセスする accessor が存在することを確認してください。

索引モデルが issue の本文から書いたものです。