Chests are part of the texture files for donkeys/mules/llamas rather than being separate files

Relates to: MC-224886 MC-279508 MC-279564 MC-279690

The bug

The chests that appear on donkeys, mules and llamas are part of the texture maps for these mobs themselves.

This is inconsistent with saddles: as of 25w03a, the saddle textures are separate files.

This results in issues such as MC-224886 and MC-279508.

How to reproduce

Check the texture files for these mobs; copies are attached.

Expected results

These textures would not include the chest textures; the chest textures would be in a separate file.

Actual results

These textures are indeed part of the file.

How to fix

Remove them from the animal textures, and relocate them to their own dedicated files. They should be applied as "equipment", much like saddles are as of 25w03a, in order to fix this issue as well as the four related issues.