Data masking(null) for column encryption

When user doesn't have permisson on a column that are encrypted by the column encryption feature (parquet-1178), returning a masked value could avoid an exception and let the call succeed.

We would like to introduce the data masking with null values. The idea is when the user gets key access denied and the user can accept null(via a reading option flag), we would return null for the encrypted columns. This solution doesn't need to save extra columns for masked value and doesn't need to translate existing data.

**Reporter**: [Xinli Shang](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=shangx@uber.com) / @shangxinli
**Assignee**: [Xinli Shang](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=shangx@uber.com) / @shangxinli

_{**Note**: *This issue was originally created as [PARQUET-2062](https://issues.apache.org/jira/browse/PARQUET-2062). Please see the [migration documentation](https://issues.apache.org/jira/browse/PARQUET-2502) for further details.*}

まず、parquet-1178 で参照されている既存の列暗号化機能と、reader のオプション処理を読みます。キーへのアクセスが拒否される経路を追跡し、null を許容する flag をどこに置くべきかを判断します。暗号化された列が、オプションが有効な場合にのみ null を返し、既存のデータに変換もマスクされた値用の追加列も必要ない状態になれば完了です。

索引モデルが issue の本文から書いたものです。