HyperTransformer Config class

[pvk-developer]

Since a Config class has been introduced to rdt.HyperTransformer and following the suggestions on this comment: #456 (comment) we should consider moving some part of the logic thats currently held by the HyperTransformer to this Config class.

Expected behavior

The Config class should be responsible for updating and validating the field_transformers, _provided_field_transformers, field_sdtypes and _provided_field_sdtypes.

Additional context

The end user should be able to work with rdt.HyperTransformer as it is now, no new api changes are required.
The Config object shouldn't be necessary for the end user to create an instance or work with the HyperTransformer.
The Config object will be generated and stored in the hypertransformer as self.config or similar variable.
From the config we will perform the rest of the calls to get or use the transformers.