BorderRadius should be stored in a field on Node not in a separate component

[ickshonpe]

All the other layout properties are stored in fields on Node, it doesn't make sense to me that BorderRadius is an exception.
It should be stored in Node in a border_radius field alongside border IMO. Internally the border radius values are ignored by Taffy and computed post Taffy's layout update but from a user's POV there's no difference.