[MC-172110] Texture of turtle shells is missing when worn by a piglin or zombified piglin

The bug

If a piglin wears a turtle shell / helmet, the turtle shell's texture is missing and an error texture is rendered instead. This also applies to their zombified variant.

Game output

Failed to load texture: minecraft:textures/models/armor/turtle_piglin_helmet.png
java.io.FileNotFoundException: minecraft:textures/models/armor/turtle_piglin_helmet.png
	at yy.a(SourceFile:67)
	at zj.a(SourceFile:67)
	at edm$a.a(SourceFile:81)
	at edm.b(SourceFile:57)
	at edm.a(SourceFile:28)
	at edr.b(SourceFile:85)
	at edr.a(SourceFile:68)
	at edr.d(SourceFile:61)
	at edr.a(SourceFile:51)
	at dud$o.a(SourceFile:205)
	at dud.a(SourceFile:32)
	at com.google.common.collect.ImmutableList.forEach(ImmutableList.java:408)
	at due$a.b(SourceFile:685)
	at dud.a(SourceFile:32)
	at due.a(SourceFile:446)
	at dtw$a.a(SourceFile:86)
	at dtw$a.getBuffer(SourceFile:45)
	at dyj.a(SourceFile:416)
	at dyj.a(SourceFile:270)
	at dtu.a(SourceFile:1330)
	at dtu.a(SourceFile:1144)
	at dtq.a(SourceFile:718)
	at dtq.a(SourceFile:543)
	at dem.d(SourceFile:1003)
	at dem.d(SourceFile:631)
	at net.minecraft.client.main.Main.main(SourceFile:204)