This change simplifies the AnnotationSync events and improves the
frame symmetry by giving the guest its own AnnotationSync setup
function, alongside its AnnotationUISync setup, that mirrors the
way its handled in the widget.

Previously, the `loadAnnotations` and `deleteAnnotations` events
were treated specially by AnnotationSync so that it didn't cause
endless loops. Instead, fully embrace the fact that the guest is
not responsible for loading or deleting annotations.

- Remove the setupAnnotation and deleteAnnotation methods, as they are
  no longer used.

- Factor out everything but the event publication of deleteAnnotation
  into a detach method that is the inverse of the anchor method.

- Subscribe to annotationsLoaded and annotationDeleted and invoke anchor
  and detach accordingly.