Fix the end of activities instead of checking compatibility between schedulers
ChoicesBuilders are meant to give all the possible choices in each state. However, when building schedulers in SchedulerGenerator we want them to take the same decision with respect to the end of each activity (when they have multiple endings).
Currently, we are checking if the choice is compatible with the current choices. However, it would be more efficient to fix the end of activity first and then generate all the possibilities for each combination of end of activities.
See method compatibleLabel in SchedulerGenerator