Fix/Refactor VillagerEntity.canBreed and wantsToStartBreeding

[Estecka]

The method VillagerEntity.canBreed returns true if the villager is unable to breed.
The method VillagerEntity.wantsToStartBreeding may sometimes return false even if the villager is willing to breed. It only returns true if the villager has twice over the amount of food required to start breeding.

In practice, these methods are only ever used to check whether two villagers should share food with each other. They're never used to trigger or prevent the actual breeding task. (The method used for that purpose is isReadyToBreed.)

I propose:
can(not)Breed -> needsFoodForBreeding
wantsToStartBreeding -> canShareFoodForBreeding

[Estecka]

Just noticed that a lacksFood also exists so I renamed it to canEatFood to avoid confusion.

needsFoodForBreeding and canShareFoodForBreeding check the villager's inventory, whereas canEatFood checks the villager's "hunger bar", and is used to consume food from the inventory.