✨ expose cache rate

[dyollb]

What do these changes do?

minor change

• expose cache rate

Related issue/s

How to test

Train with new option cache_rate, e.g.

{
    "image_dir": "F:\\TrainMelanie\\T1_on_T2\\MRI",
    "labels_dir": "F:\\TrainMelanie\\T1_on_T2\\Labels",
    "tissue_list": "F:\\TrainMelanie\\T1_on_T2\\labels.txt",
    "output_dir": "F:\\TrainMelanie\\T1_on_T2\\Model",
    "num_channels": 2,
    "spatial_dims": 3,
    "spatial_size": null,
    "max_epochs": 600,
    "cache_rate": 0.4,
    "save_nifti": true,
    "gpu_ids": [
        0
    ]
}

Checklist

• [x] Non-breaking change (fix or new feature that would not break existing functionality).