refactor(srp): move universal backend ownership into renderer data

managed/XCEngine.ScriptCore/Rendering/Universal/UniversalRendererData.cs

@@ -22,6 +22,11 @@ namespace XCEngine.Rendering.Universal
             return rendererFeatures ??
                    Array.Empty<ScriptableRendererFeature>();
         }
+
+        protected override string GetPipelineRendererAssetKey()
+        {
+            return "BuiltinForward";
+        }
     }
 }