Allow configurable living entity (non-persistant) despawn ranges

This PR allows users to change the hard (instant despawning) and soft (chance at despawning) despawn range on non-persistent, living entities, allowing for changes to gameplay, either to make mobs seems like they are more frequently around the player or more persistent in the world.

Lowing the hard despawn to 90 (to cover all of the possible area, 60 to be fully within the area) would mean mobs would only be within the area that mobs can spawn around the players (Assuming default spawn distance of 4 chunks) or lowered even further to make them seem even more frequent (though lowering the hard to below 24 will cause no spawns).

This also allows for increasing of both hard and soft to make the world feel more persistent or prevent the despawn mobs in a custom setup/dungeon without using persistence nbt tags..