Added metrics for BraTS Path challenge

[sarthakpati]

Fixes #817

Proposed Changes

• auroc has been fixed
• added matthews correlation coefficient (mcc) from torchmetrics
• changed output format to json (YAML was giving issues with mcc)
• updated output dict of metrics to ensure that the averaging types are not overwritten
• TODO: add tests using binary classification so that auroc gets tested

Checklist

• CONTRIBUTING guide has been followed.
• PR is based on 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 (ensure typing is used to provide type hints, including and not limited to using Optional if a variable has a pre-defined value).
• Code has been blacked for style consistency and linting.
• If applicable, version information has been updated in GANDLF/version.py.
• If adding a git submodule, add to list of exceptions for black styling in pyproject.toml file.
• Usage documentation has been updated, if appropriate.
• Tests added or modified to cover the changes; if coverage is reduced, please give explanation.
• If customized dependency installation is required (i.e., a separate pip install step is needed for PR to be functional), please ensure it is reflected in all the files that control the CI, namely: python-test.yml, and all docker files [1,2,3].

[github-actions]

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[szmazurek]

I believe it is fine now, good idea with adding average type to the metric name. LGTM

[sarthakpati]

Thanks for the review, @szmazurek!

I will wait for @Geeks-Sid and @vpchung to test this before merging.

[sarthakpati]

The test failure is related to #889.