change the group slot value of the animal depending of it's growth stage

PoT also has a group system relying on Slots and group value of the playables, which might lead to some problems when nesting is implemented (if the baby has the same group value as their adult counterparts)

Thus I propose to change the slot value of the animals according to their growth stage, starting at 0 for the hatchlings (when they just got out of the egg) and maxing at the adult value when they reach adulthood, adjusting the slot value of the character whenever it reaches another step in it's growth

Thus, very vulnerable babies will be able to receive all the parental care they may require, regardless of the specie, but when they grow up to a certain point they'll eventually have to split from their parents

I believe this would help organise groups in the future, when nesting and growth have been added, and prevent players yeeting their baby surplus into the wilderness to save up group space (except for species designed for this kind of gameplay, like turtles for example)