Add Machine Learning Challenges

[pvk-developer]

Description

Improve benchmark module by adding Machine Learning based challenges.

With the following developing improvements proposed:

• Change challenges to return a dictionary with the hyperparameters get_tunable_hyperparameters instead of get_tunable, this way the challenges can be used by other libraries.
• Create a MLChallenge class to be used as a parent.
• Use MLChallenge class to load the dataset, split and train a machine learning model.
• Evaluate with a cross_validate.