Collider debug lines are rendered behind the model

For some reason collider debug lines are always rendered behind geometry. This is especially bad when "ground" mesh is present because it completely covers debug lines.

Regular plugins init:
```rust
.add_plugin(RapierDebugRenderPlugin {
enabled: true,
always_on_top: true,
..default()
})
```

Adding rapier stuff when scene is loaded (in my case I need to add it only after snene is available):
```rust
commands.entity(entity)
.insert(RigidBody::Fixed)
.insert(Collider::cuboid(1.0, 0.5, 1.0))
.insert(ColliderDebugColor(Color::CYAN))
.insert(SceneBundle { scene: hull.default_scene.clone().unwrap(), ..default() })
```

And here is a result:

https://user-images.githubusercontent.com/1215187/225895577-b1871e92-7431-4671-93ea-c24985e874c5.mov

Reproduce the issue with RapierDebugRenderPlugin configured with always_on_top and a ground mesh, using the scene-loading example in the report. Start by tracing the debug renderer's depth or draw-order handling; done means collider debug lines remain visible in front of geometry when always_on_top is true.

Written by the indexing model from the issue text.