* Refactor previous tests for shared resources
* Add validation result models
This also includes a method for merging them, useful when running validation in batches
* Added `DataFrameValidationEngine` for running tests
This also includes a registry for mapping test names to pandas test classes
* Implement the DataFrameValidator facade
This includes the logic to load tests from different sources (OpenMetadata or code) and pass them down to the engine.
It also includes tests for the integration with OpenMetadata
* Add examples for the API
* Apply comments
