VanillaBackport X Incubation Compat

• Added data-driven chicken variant support (similar system to the one used by Eggcelent)
• Minor change to the textures of the blue and brown egg crates
• Removed some redundant code and refactored it

Chicken variants added via datapack can now lay brown or blue eggs if they are registered in their respective tags: #minecraft:spawns_warm_variant_farm_animals for brown eggs, and #minecraft:spawns_cold_variant_farm_animals for blue eggs, or any other tag for temperate eggs.