Rewrite VIFp metric

## Feature Request

### Description

Rewrite the VIFp metric to be usable for 3D data.

### Use cases

VIFp can be used for 3D data.

### Possible implementation

Use original MATLAB code for VIFp as reference.

### Alternative solutions

The issue mentions using original MATLAB code for VIFp as reference. First, locate the existing VIFp implementation in the repository, likely in a metrics module. Understand the current 2D approach, then study the MATLAB reference to adapt it for 3D data. Testing will involve volumetric image data to verify correctness.

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