Mesh Utils

My mesh merging utilities.

Also contains A port of https://github.com/Whinarn/UnityMeshSimplifier to a GODOT engine c++ module.

For future reference it's based on e8ff4e8862735197c3308cfe926eeba68e0d2edb.

Porting is mostly done, but it does needs some debugging (it has a crash if smart linking is enabled).