- 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
- bridge renderer list descriptors into ScriptableRenderContext scene draw calls
- reuse DrawObjectsPass across Universal and project custom renderers
- add RenderObjectsRendererFeature for package-level object draw extension
