Enable custom collider shapes

[PixelDust22]

This PR proposes some changes to enable custom colliders in bevy_rapier.

Requires dimforge/parry#217
Requires dimforge/parry#216

[ThierryBerger]

Thanks ! the diff looks appealing ! More features less code 👍

I'd love an example and a changelog line to accompany this

[ThierryBerger]

if I'm understanding correctly, a good information to add here would by the number identifying the shape ?

maybe as_typed_shape() would be interesting ?

Suggested change

	ColliderView::Custom(_) => write!(f, "Custom"),
	ColliderView::Custom(shape) => write!(f, "{:?}", shape.as_typed_shape()),

[PixelDust22]

This wouldn’t be very useful because as_typed_shape would just return TypedShape::Custom which now contains a &dyn Shape instead after dimforge/parry#216.
Unfortunately, we don’t know if the custom shape implements Debug.

We’re getting rid of the number identifying the custom shape because it’s not very useful. Instead, the user should use downcasts in their custom QueryDispatcher.

The PR allowing custom QueryDispatcher is incoming.

[PixelDust22]

Note that this isn’t really less code, I just think that it’s a better idea to move the scaling code to the rapier::Shape trait so that custom shapes can more easily implement its own logic about scaling.

On example and changelog: We can add the examples after I put out the PR for custom QueryDispatcher.

[PixelDust22]

@Vrixyz This should be ready to merge now.