Include legs as part of the Harness texture

I've been working on a Resource Pack, and while making my edits to the Happy Ghast's Harnesses, I noticed that despite the texture sharing a layout with the base Ghast texture, the Harness's texture only covers the head when rendered in game.

Contrast this with something like the Horse's Saddle or the Llama's Carpet for example, which are able to cover the entire mob despite the base game's texture only covering certain parts of their respective mob, allowing for extra customization.

It doesn't really make much sense for this not to be the case for the Happy Ghast's Harnesses as well, as currently it seems more like an arbitrary restriction and a rather limiting one at that given how it effectively means that the only parts of the texture that is customizable are the head and the goggles.