Rename CountsPredictor and modernize its API for consistency with MapEvaluator

Rename CountsPredictor and modernize its API for consistency with MapEvaluator: a task in MiMo-V2.6-RL-harbor-code: MiMo-V2.6-RL Code (Harbor) (Harbor dataset). Right now we have two classes that essentially do the same job — compute predicted counts ( npred ) from a model and a set of IRFs — but…