Decouple `PointerId` and `PointerKind`

When making a custom ID'd pointer, it is also desired to be able to specify what *kind* of pointer it is, because application logic can change based on this. Today, these two are coupled.

Pointers do not use the Entity as an ID, because lifting the pointer despawns the entity, and the pointer being controlled needed a stable ID. It's possible we can solve this problem today, or just use a UUID under the hood for all pointers that is stable between pointers lifting.