[C++][Parquet] Deprecated BIT_PACKED level decoding is probably incorrect

In working on PARQUET-1652, I noticed that our implementation of BIT_PACKED almost certainly does not line up with apache/parquet-format. I'm going to disable it in our tests until it can be validated

**Reporter**: [Wes McKinney](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=wesm) / @wesm

_{**Note**: *This issue was originally created as [PARQUET-1653](https://issues.apache.org/jira/browse/PARQUET-1653). Please see the [migration documentation](https://issues.apache.org/jira/browse/PARQUET-2502) for further details.*}