Tests needed in DVT for Latin characters (ISO-8859) in Oracle, DB2 and PostgreSQL

Hi,

The encoding for character strings in Oracle, DB2 and Postgres is set at the database level and currently default to UTF-8. We do not know if DVT works correctly if the encoding for character strings is ISO-8859 character set.

Recommendation is to create the [table dvt_latin](https://github.com/GoogleCloudPlatform/professional-services-data-validator/blob/781490658875f6dab128f11c1a1af325561788fc/tests/resources/bigquery_test_tables.sql#L159) in a database with encoding set to ISO-8859. This can be row validated with BigQuery. This is the only test that is needed with this encoding.

Since this is a different database, it will require separate credentials and likely another test run (?)

Thanks.

Sundar Mudupalli