iris: fold render state into Ui

tests/color_space.rs

@@ -51,12 +51,7 @@ fn solid_paints_and_images_round_trip_through_an_srgb_target() {
 }
 
 fn render(gpu: &Gpu, renderer: &mut UiRenderNode, harness: &mut Harness) -> [[u8; 4]; 2] {
-    renderer.update(
-        &gpu.device,
-        &gpu.queue,
-        &mut harness.rsc.ui,
-        &mut harness.render,
-    );
+    renderer.update(&gpu.device, &gpu.queue, &mut harness.rsc.ui);
     let texture = gpu.device.create_texture(&wgpu::TextureDescriptor {
         label: Some("Iris colour-space target"),
         size: wgpu::Extent3d {