Metrics Refactor

[bogdansurdu]

This PR will make the following changes:

NEW MODULES

• Create and move correlation metrics to the module (correlation_metrics.py) in the fairlens.metrics package. Metrics will now be shared between heatmap.py and the proxy detection in 'correlation.py' from the detection module
• Create and move statistical distance metrics to the module (distance_metrics.py) in the fairlens.metrics package
• Add statistical distance base classes (i.e. ContinuousDistanceMetric) to distance_metrics.py as well

CHANGED MODULES

• Remove statistical distance implementations from the old metrics.py module and leave only auto_distance and stat_distance as the main functionality used by the fairness scorer
• Rename old metrics.py module to distance.py to better reflect its purpose
• Restructure test_metrics.py and test_distance.py imports to point to the new location of the metrics

REMOVED MODULES

• Remove old distance.py module (which contained the statistical distance abstract and base classes)

[sonarcloud]

SonarCloud Quality Gate failed.   

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0.0% Duplication

[rob-tay]

Closing as this has been superseded by #67 #69