SYSML2_ — Stakeholder_Mapping should map from Classifier to PartDefinition

The SysML v1 stereotype Stakeholder is applied to Classifiers. Therefore, it could also be other model elements than Class which represent stakeholders. The usage of Actor is quite common.

Actors are mapped to PartDefinition. Therefore, Stakeholders should also be mapped to PartDefinition which makes it more consistent. Stakeholders and Actors are different concepts, but there seems to be no reason to map them differently to parts and items.