Add missing #[reflect(Component, Default)] to SceneRoot and DynamicSceneRoot. (#16816)

Someone forgot to add these, and I need them since I spawn these
components in my [glXF] files.

[glXF]: https://github.com/pcwalton/bevy-glxf-loader/

Author: pcwalton

crates/bevy_scene/src/components.rs

@@ -1,7 +1,7 @@
 use bevy_asset::Handle;
 use bevy_derive::{Deref, DerefMut};
-use bevy_ecs::component::Component;
-use bevy_reflect::Reflect;
+use bevy_ecs::{component::Component, prelude::ReflectComponent};
+use bevy_reflect::{prelude::ReflectDefault, Reflect};
 use bevy_transform::components::Transform;
 use derive_more::derive::From;
 
@@ -13,13 +13,15 @@ use crate::{DynamicScene, Scene};
 /// Adding this component will spawn the scene as a child of that entity.
 /// Once it's spawned, the entity will have a [`SceneInstance`](crate::SceneInstance) component.
 #[derive(Component, Clone, Debug, Default, Deref, DerefMut, Reflect, PartialEq, Eq, From)]
+#[reflect(Component, Default, Debug, PartialEq)]
 #[require(Transform)]
 #[cfg_attr(feature = "bevy_render", require(Visibility))]
 pub struct SceneRoot(pub Handle<Scene>);
 
 /// Adding this component will spawn the scene as a child of that entity.
 /// Once it's spawned, the entity will have a [`SceneInstance`](crate::SceneInstance) component.
 #[derive(Component, Clone, Debug, Default, Deref, DerefMut, Reflect, PartialEq, Eq, From)]
+#[reflect(Component, Default, Debug, PartialEq)]
 #[require(Transform)]
 #[cfg_attr(feature = "bevy_render", require(Visibility))]
 pub struct DynamicSceneRoot(pub Handle<DynamicScene>);