ChickenLayingRework

• Fixed chickens occasionally disappearing after restarting and reopening a world.
• Fixed a synced entity-data crash when loading or spawning chickens.
• Fixed crashes involving chicken jockey creation.
• Chicken ready-to-lay state now persists across world and server restarts.
• Invalid saved variant data now safely falls back to the default state.
• Improved compatibility with mods that add synced data to chickens.

Previously lost chickens cannot be restored automatically; this update prevents future losses.