Move parse_tokens

parse_tokens is used at multiple places in the lib. We should move it way higher in https://gitlab.teklia.com/atr/dan/-/blob/main/dan/utils.py

changed milestone to %DAN-P5: Improve training

added P3 Quick Win labels

assigned to @yschneider

mentioned in merge request !240 (merged)

closed with merge request !240 (merged)