add metrics mlcube for brasyn challenge with two pre-trained nnUNet

[WinstonHuTiger]

In order to add the support to segment the metastasis and glioma, I trained two nnUNet based on Brats-2024's Brain Metastases and Brats-2021 glioma dataset. The original docker image is located at my winstonhutiger/brasyn_nnune.

The MLCube can be built as usual. No pre-installation is required.

[github-actions]

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