use scene names if they exist

[ChristopherBiscardi]

Objective

glTF scenes often have names. Our loader code does not insert them. This results in tools like bevy_inspector_egui showing Entity on the scene's root entity instead of "MyPlayerScene" or whatever it was named in blender, etc.

Solution

Use names if they exist, otherwise use a default name based on the glTF index of the scene which mirrors other usage.

Testing

I loaded models/FlightHelmet/FlightHelmet.gltf and models/cube/cube.gltf into the 3d_scene example and wrote a small system to check for the existence of Name components. With this patch, the Scene and Scene0 names will log out (FlightHelmet doesn't have a name, so will print Scene0 while cube has a name, which is Scene without the index).

fn update(query: Query<&Name>) {
    for item in &query {
        dbg!(item);
    }
}