Split the 4 legs of a pig's UV map into their own sections for RPs

This idea comes from the resolution of https://bugs.mojang.com/browse/MC-274246

Now that the pig has 2 new textures, and the UV map was expanded from 32x64 to 64x64, it would be a good idea to better improve the UV map by splitting the four legs of the pig into their own sections on the UV map. This would allow maximum customization of the pigs texture in resource packs.