Validation of non existent columns quietly ignored

Hi,

When users request validation of non existent columns, the validation for that column is quietly ignored.

1. DVT should minimally log a WARNING - so customers know the the validation column they requested does not exist. Logging an error could break current validations.

To demonstrate try this command `data-validation validate column -sc oracle21 -tc postgres -count='col_baa' tbls=pso_data_validator.dvt_core_types=pso_data_validator.dvt_core_types` or this `data-validation validate row -sc oracle21 -tc postgres -hash='col_date,col_baa' -pk=id -tbls=pso_data_validator.dvt_core_types=pso_data_validator.dvt_core_types`

2. This may require updates to our test suites - since they don't expect the warning.

Thanks.

Sundar Mudupalli