Scan: Add a robustness detector to the scan that perturbs numerical values

[kevinmessiaen]

🚀 Feature Request

Add a robustness detector to the scan that perturbs numerical values.

The scan should be able to a set of issues that capture the minimum amount of perturbation (lying in the bounds of the feature distribution) needed on a single numerical feature to:

• (a) change the predicted label (classification)
• (b) change the prediction by an amount that exceeds a certain threshold (regression)

🔈 Motivation

Currently the scan does not have any numerical perturbation.