Added a few segmentation metrics

[sarthakpati]

Fixes #660

Proposed Changes

• added metrics for segmentation to enhance interpretation of results

Checklist

• I have read the CONTRIBUTING guide.
• My PR is based from the current GaNDLF master .
• Non-breaking change (does not break existing functionality): provide as many details as possible for any breaking change.
• Function/class source code documentation added/updated.
• Code has been blacked for style consistency.
• If applicable, version information has been updated in GANDLF/version.py.
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• Usage documentation has been updated, if appropriate.
• History has been updated, if appropriate.
• Tests added or modified to cover the changes; if coverage is reduced, please give explanation.
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[github-actions]

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Waiting for multi-dim tests

[sarthakpati]

Since the tests in #663 are passing, do you need me to make them work for this as well? Once that PR is merged, this will get automatically closed.