[SSL] Port over transforms associated with ContextPrediction and ContextRestoration

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Add the transformations required to perform Context Prediction and Context Restoration

TODOs

• Add CoarseDropout
• Add SwapPatches
• Add FillRegionsWithValue
• Add Swap2DPatches

Source: https://github.com/jeffreydominic/MedSegPy/blob/context_encoder/medsegpy/data/transforms/transform_gen.py