Move mesh code to shared base class and reordanize files

Source/Engine/Graphics/Models/Model.cs

@@ -0,0 +1,22 @@
+// Copyright (c) 2012-2024 Wojciech Figat. All rights reserved.
+
+namespace FlaxEngine
+{
+    partial class Model
+    {
+        /// <summary>
+        /// The maximum amount of levels of detail for the model.
+        /// </summary>
+        public const int MaxLODs = 6;
+
+        /// <summary>
+        /// The maximum amount of meshes per model LOD.
+        /// </summary>
+        public const int MaxMeshes = 4096;
+
+        /// <summary>
+        /// The maximum allowed amount of material slots per model resource
+        /// </summary>
+        public const int MaxMaterialSlots = 4096;
+    }
+}