ENH Add mitigation algorithm from "Optimized Pre-Processing for Discrimination Prevention" by Calmon et al.

The paper Optimized Pre-Processing for Discrimination Prevention by Calmon et al. introduces a preprocessing algorithm for demographic parity while limiting the number of individual distortions. The goal of this task is to add the algorithm described in this paper to Fairlearn.

• The original implementation by the authors of the paper can be found here.
• An existing implementation can be found in AIF360 OptimPreproc.

Completing this item requires:

• technique code in fairlearn.preprocessing
• unit tests in test.unit.preprocessing
• descriptive API reference (directly in the docstring)
• a short user guide in docs.user_guide.mitigation.rst

A fully fledged example notebook is not required.

To claim this task please respond below. Of course, you can also ask questions!