Updating a `Collider` through one of the `**_mut()` method doesn't work

When I update a `Collider` component, using one of the `**_mut()` methods such as `as_cone_mut()`, I find that the collider is never updated. Instead, I have to clone the `SharedShape` of the `Collider` using the `Shape::clone_box` method and replace the `raw` field of `Collider`.

It probably happens because somewhere, update is dependent on `Arc` pointer comparison instead of structural comparison. A good way of working around that is to make the `set` methods of the various `**ViewMut` set a "update" field in `Collider`, and use that field in addition to the pointer comparison for update detection.