Mesh Helper multi-mesh support (#241)

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## [SDK-524](https://ready-player-me.atlassian.net/browse/SDK-524)

## Description

- Mesh helper now supports transfer from multiple source mesh, material
and bones target

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-->
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## How to Test

- Load atlassed and non-atlassed avatars with different customization
combinations in Photon Sample project

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## Checklist

-   [ ] Tests written or updated for the changes.
-   [ ] Documentation is updated.
-   [x] Changelog is updated.

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[SDK-524]:
https://ready-player-me.atlassian.net/browse/SDK-524?atlOrigin=eyJpIjoiNWRkNTljNzYxNjVmNDY3MDlhMDU5Y2ZhYzA5YTRkZjUiLCJwIjoiZ2l0aHViLWNvbS1KU1cifQ

Author: srcnalt

CHANGELOG.md

@@ -3,6 +3,12 @@
 All notable changes to this project will be documented in this file.
 This project adheres to [Semantic Versioning](http://semver.org/).
 
+
+## [6.0.2] - 2024.MM.DD
+
+### Updated
+- AvatarMeshHelper now supports multiple mesh and material transfer. [#241](https://github.com/readyplayerme/rpm-unity-sdk-core/pull/241)
+
 ## [6.0.1] - 2024.02.26
 
 ### Updated

Runtime/Core/Scripts/Utils/AvatarMeshHelper.cs

@@ -1,29 +1,68 @@
 using UnityEngine;
+using System.Collections.Generic;
 
 namespace ReadyPlayerMe.Core
 {
     public static class AvatarMeshHelper
     {
+        [Obsolete("Use TransferMesh(GameObject source, GameObject target) instead.")]
         public static void TransferMesh(GameObject source, SkinnedMeshRenderer[] targetMeshes, Animator targetAnimator)
         {
-            var sourceAnimator = source.GetComponentInChildren<Animator>();
-            SkinnedMeshRenderer[] sourceMeshes = source.GetComponentsInChildren<SkinnedMeshRenderer>();
-            for (var i = 0; i < targetMeshes.Length; i++)
+            TransferMesh(source, targetMeshes[0].transform.parent.gameObject);
+        }
+        
+        /// <summary>
+        ///     Transfers the mesh and material data from the source to the target avatar.
+        /// </summary>
+        /// <param name="source">Imported Ready Player Me avatar.</param>
+        /// <param name="target">Photon Network Player Character.</param>
+        public static void TransferMesh(GameObject source, GameObject target)
+        {
+            // store the relevant data of the source (downloaded) avatar
+            var rendererDict = new Dictionary<string, SkinnedMeshRenderer>();
+            
+            var sourceRenderers = source.GetComponentsInChildren<SkinnedMeshRenderer>();
+            var targetRenderers = target.GetComponentsInChildren<SkinnedMeshRenderer>();
+            
+            foreach (var renderer in sourceRenderers)
+            {
+                rendererDict.Add(renderer.name, renderer);
+            }
+            
+            // transfer the data to the target skinning mesh renderers
+            foreach (var renderer in targetRenderers)
             {
-                if (i >= sourceMeshes.Length)
+                if (rendererDict.TryGetValue(renderer.name, out var sourceRenderer))
                 {
-                    targetMeshes[i].enabled = false;
-                    break;
+                    renderer.material = sourceRenderer.materials[0];
+                    renderer.sharedMesh = sourceRenderer.sharedMesh;
+                    
+                    // transfer the bone data
+                    foreach (var targetBone in renderer.bones)
+                    {
+                        foreach (var sourceBone in sourceRenderer.bones)
+                        {
+                            if (sourceBone.name == targetBone.name)
+                            {
+                                targetBone.position = sourceBone.position;
+                                targetBone.rotation = sourceBone.rotation;
+                                targetBone.localScale = sourceBone.localScale;
+                                break;                            
+                            }
+                        }
+                    }
+                }
+                else
+                {
+                    // remove the renderer if it's not found in the source avatar
+                    Object.Destroy(renderer.gameObject);
                 }
-                Mesh mesh = sourceMeshes[i].sharedMesh;
-                targetMeshes[i].sharedMesh = mesh;
-                targetMeshes[i].enabled = true;
-                Material[] materials = sourceMeshes[i].sharedMaterials;
-                targetMeshes[i].sharedMaterials = materials;
             }
-
-            Avatar avatar = sourceAnimator.avatar;
-            targetAnimator.avatar = avatar;
+            
+            // transfer the animation avatar
+            var sourceAnimator = source.GetComponentInChildren<Animator>();
+            var targetAnimator = target.GetComponentInChildren<Animator>();
+            targetAnimator.avatar = sourceAnimator.avatar;
         }
     }
 }