feat(srp): add shader pass selection for scene draws

- let DrawingSettings carry an optional shaderPassName across managed and native scene draw APIs
- allow RenderObjectsRendererFeature to author explicit ForwardLit or Unlit scene draws
- exercise the new scene draw pass selection seam in the project render pipeline probe

project/Assets/Scripts/ProjectRenderPipelineProbe.cs

@@ -139,6 +139,8 @@ namespace ProjectScripts
                                 RenderPassEvent.RenderOpaques,
                             scenePhase =
                                 SceneRenderPhase.Opaque,
+                            shaderPassName =
+                                "Unlit",
                             overrideMaterialPath =
                                 "Assets/New Material.mat",
                             overrideRenderQueueRange = true,