Implement the methods of RapierContext on RapierContextItem instead

[idanarye]

RapierContext has various methods that can be used to query the simulated world. Problem is - you never actually get a value (or even reference) of the type RapierContext. Bevy queries don't return the item itself - instead they return its QueryData::Item. In our case - it's RapierContextItem, which is generated automatically by the #[derive(query::QueryData)] and does not have any of these methods, making them unusable.

If these methods were implemented on RapierContextItem instead of RapierContext (which should be doable even if RapierContextItem itself is generated by a macro) then Query<&RapierContext> would be usable (currently it isn't)