There is overlap between ValidTypeMap and PrimitiveTypeName in parquet-mr

It might be a good idea to unify these two classes

**Reporter**: [Alex Levenson](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=alexlevenson) / @isnotinvain

_{**Note**: *This issue was originally created as [PARQUET-30](https://issues.apache.org/jira/browse/PARQUET-30). Please see the [migration documentation](https://issues.apache.org/jira/browse/PARQUET-2502) for further details.*}

Start by locating and comparing ValidTypeMap and PrimitiveTypeName in parquet-mr to document their overlapping responsibilities. Before changing either class, determine the intended unified API and identify the existing tests that cover both types. Done means the overlap is removed without changing the supported type behavior, but this issue does not define the design or acceptance criteria.

Written by the indexing model from the issue text.