GAN metrics

[szmazurek]

Is your feature request related to a problem? Please describe.

Add new metrics that will be used in evaluation of generative networks

Describe the solution you'd like

Implementation for the most common used metrics as fid, lpips, ssim

Describe alternatives you've considered

Utilizing existing synthesis metrics (may integrate in the future, for now I think it would be good to keep them separate)

Additional context

Add any other context or screenshots about the feature request here.