Initial VRM Conversion

VRM Conversion, converts the vrm armature and removes colliders as there are not used in Unity. There some bugs and i need to optimise it and etc. Also we need to remove root empty bone as it's useless in Unity.

Ran out of time to finish it but proof of concept it works lol. However dont want to release it unto Alpha 4 as it need to be tested and i may seperate some things into different buttons but i have not decided.

core/properties.py

@@ -608,6 +608,13 @@ class AvatarToolkitSceneProperties(PropertyGroup):
         update=update_log_level
     )
 
+    # VRM Conversion Properties
+    vrm_remove_colliders: BoolProperty(
+        name="Remove Colliders",
+        description="Remove VRM collider bones during conversion",
+        default=True
+    )
+
 def register() -> None:
     """Register the Avatar Toolkit property group"""
     logger.info("Registering Avatar Toolkit properties")