Invisible donkeys, mules and llamas do not display their chests

Relates to: MC-13738 MC-224886

The bug

MC-13738 was fixed in 25w03a to make saddles show up on invisible donkeys and mules. However, this fix does not extend to chests.

As chests are not physically part of a donkey or mule's body, they should not be considered as such when the mob is in an invisible state.

How to reproduce

1. Add a chest to a donkey or mule

2. Give it the invisibility effect

Expected results

The chest would remain visible even though the donkey itself wouldn't be.

Actual results

The chest goes invisible as well.

How to fix

Split the chest off into its own texture file and make it use the equipment system, like was done for saddles in this snapshot.