Updated the metrics output

[sarthakpati]

Fixes #686

Proposed Changes

• metrics that were getting encoded as lists will now show as string separated using _ (we can change this as requirements change in the future)
• added a single function to collect, format, and print the metrics

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.
• If adding a git submodule, add to list of exceptions for black styling in pyproject.toml file.
• 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.
• 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]

MLCommons CLA bot All contributors have signed the MLCommons CLA ✍️ ✅

[codecov]

Codecov Report

Merging #687 (1bcc4af) into master (29e4560) will decrease coverage by 0.01%.
The diff coverage is 100.00%.

❗ Current head 1bcc4af differs from pull request most recent head c233c3b. Consider uploading reports for the commit c233c3b to get more accurate results

@@            Coverage Diff             @@
##           master     #687      +/-   ##
==========================================
- Coverage   94.62%   94.61%   -0.01%     
==========================================
  Files         116      116              
  Lines        8054     8062       +8     
==========================================
+ Hits         7621     7628       +7     
- Misses        433      434       +1     

Flag	Coverage Δ
unittests	94.61% <100.00%> (-0.01%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
GANDLF/utils/__init__.py	100.00% <ø> (ø)
GANDLF/compute/forward_pass.py	93.58% <100.00%> (-0.17%)	⬇️
GANDLF/compute/training_loop.py	83.11% <100.00%> (-0.43%)	⬇️
GANDLF/utils/generic.py	90.65% <100.00%> (+2.14%)	⬆️

... and 1 file with indirect coverage changes

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