mounts of mayhem part 2

add polar bear rider with a new frozen zombie variant, fix the spear's hitbox bug in java edition, and also add villager guardians(new villager profession) , and they might be 1 of 3 types: normal guard(holds a sword and a shield, sword upgrades with trade level), knight guard(rides a horse with a spear, spear upgrades with trade level), and bodyguard(only guards a villager of your choice, uses axe and can take dmg for the villager, health increases with trade level)all of them has iron armor. and the frozen zombie variant holds a shield.