Wither armor animation is hardcoded

Relates to: MC-276497 MC-277503 MC-277519 MC-278361

The bug

The armor animation used for withers does not use an associated .mcmeta file, unlike almost all other animated textures in the game, including animated entity textures such as conduits.

How to fix

Introduce a .mcmeta file for armored withers like what exists for all other animated textures in the game.