Closes #2896

- Fixed issue where Actor built in components could not be extended because of the way the Actor based type was built.
  - Actors now use instance properties for built-ins instead of getters
  - With the ECS refactor you can now subtype built-in `Components` and `.get(Builtin)` will return the correct subtype.
  ```typescript
  class MyBodyComponent extends ex.BodyComponent {}

  class MyActor extends ex.Actor {
      constructor() {
        super({})
        this.removeComponent(ex.BodyComponent);
        this.addComponent(new MyBodyComponent())
      }
  }

  const myActor = new MyActor();
  const myBody = myActor.get(ex.BodyComponent); // Returns the new MyBodyComponent subtype!
  ```