Add a test to figure out the value of `collider` from `intersect_ray`

[Demindiro]

While reading the Godot documentation I noticed that the keys in the returned are called collider and collider_id. However, AFAICT there is no way to set an object/instance ID per collider/shape. You can only do this per Body/Area.

While the function seems to work as expected a test should be added to ensure it actually matches the Bullet behaviour.

[Demindiro]

I just checked some other code of mine and it clearly relies on intersect_ray returning a reference to a RigidBody. I suppose Godot's documentation should be updated then.

[Demindiro]

I'm going to close this since this is purely an issue with Godot's documentation.