Fix extra-dark cracking animation where multiple model planes coincide

[muzikbike]

Request Description

Vanilla issue https://bugs.mojang.com/browse/MC-268537. Much the same as #2447 and I presume the underlying cause is the same.

Compare the cracking animation on a wall (four ways with central pillar) breaking viewed from below versus a normal block of that same material:

The proposed fix might work here as well although I don't know how it could be made to work for multiparts.