Save metrics results to YAML instead of plain text

Closes #70 (closed)

Numpy types (float/int64) cannot be exported directly to YAML. I had to convert the metrics to int/float to be able to export them. This manager will be refactored later so imo it's okay to add a little bit more complexity there.

changed milestone to %DAN-P2: Clean code and remove unused code

added P2 Quick Win labels

requested review from @melodie.boillet

assigned to @schneider-y

Seems good to me

approved this merge request

@schneider-y Please rebase

added 2 commits

• 24b5eb14 - 1 commit from branch main
• 6c8cecdd - format results to primitive types (no numpy allowed in YAML)

Compare with previous version

merged