Improve consistency of trait parsing phases

[csoltenborn]

Traits added via our custom macros work additively, i.e., it's possible to assign e.g. two Author traits. However, this is not possible for regex-assigned tests...

This enhancement will change the traits assigned to tests if more than one trait is assigned via the Before test discovery and After test discovery options such that more than one trait with the same name is assigned in one of the phases.