Enhance unit testing by generating the data types for tables using columnMetadataGen instead

[cbarca]

...of which cols will map to Spark types anyways, but at least, now that we refactored the ColumnMetadata class with the addition of VectorDataTypes, we can test our serialization/deserialization starting from the Vector/SQL types in order to cover other properties (such as specific precision, scale, etc)

[justinegdelta]

This commit is the first step toward consolidating and normalizing the metadata generation of vector types.
2f2fa6f