feat(srp): add drawing settings override material seam

- add a managed DrawingSettings seam for scene draw authoring
- let builtin forward scene draws use an override material when provided
- wire DrawObjectsPass and RenderObjectsRendererFeature through the new settings

managed/XCEngine.ScriptCore/Rendering/Core/ScriptableRenderContext.cs

@@ -67,22 +67,47 @@ namespace XCEngine.Rendering
         public bool DrawRenderers(
             SceneRenderPhase scenePhase,
             RendererListType rendererListType)
+        {
+            return DrawRenderers(
+                scenePhase,
+                rendererListType,
+                DrawingSettings.CreateDefault());
+        }
+
+        public bool DrawRenderers(
+            SceneRenderPhase scenePhase,
+            RendererListType rendererListType,
+            DrawingSettings drawingSettings)
         {
             return DrawRenderers(
                 scenePhase,
                 RendererListDesc.CreateDefault(
-                    rendererListType));
+                    rendererListType),
+                drawingSettings);
         }
 
         public bool DrawRenderers(
             SceneRenderPhase scenePhase,
             RendererListDesc rendererListDesc)
+        {
+            return DrawRenderers(
+                scenePhase,
+                rendererListDesc,
+                DrawingSettings.CreateDefault());
+        }
+
+        public bool DrawRenderers(
+            SceneRenderPhase scenePhase,
+            RendererListDesc rendererListDesc,
+            DrawingSettings drawingSettings)
         {
             return InternalCalls
                 .Rendering_ScriptableRenderContext_DrawRenderersByDesc(
                     m_nativeHandle,
                     (int)scenePhase,
-                    ref rendererListDesc);
+                    ref rendererListDesc,
+                    drawingSettings.overrideMaterialPath ??
+                        string.Empty);
         }
 
         public bool RecordOpaqueScenePhase()