feat(rendering): select managed SRP through asset instances

managed/XCEngine.ScriptCore/GraphicsSettings.cs

@@ -4,31 +4,10 @@ namespace XCEngine
 {
     public static class GraphicsSettings
     {
-        public static Type renderPipelineAssetType
+        public static ScriptableRenderPipelineAsset renderPipelineAsset
         {
-            get
-            {
-                string assemblyQualifiedName =
-                    InternalCalls.Rendering_GetRenderPipelineAssetTypeName();
-                if (string.IsNullOrEmpty(assemblyQualifiedName))
-                {
-                    return null;
-                }
-
-                return Type.GetType(assemblyQualifiedName, throwOnError: false);
-            }
-            set
-            {
-                if (value != null &&
-                    !typeof(ScriptableRenderPipelineAsset).IsAssignableFrom(value))
-                {
-                    throw new ArgumentException(
-                        "GraphicsSettings.renderPipelineAssetType must derive from ScriptableRenderPipelineAsset.",
-                        nameof(value));
-                }
-
-                InternalCalls.Rendering_SetRenderPipelineAssetType(value);
-            }
+            get => InternalCalls.Rendering_GetRenderPipelineAsset();
+            set => InternalCalls.Rendering_SetRenderPipelineAsset(value);
         }
     }
 }