Previously there were three public methods for setting the selected annotations
in the sidebar and opening it, but only one was used outside of `Guest`
and there was an inconsistency when toggling vs selecting normally.

 - Combine the `showAnnotations`, `toggleAnnotationSelection` and
   `selectAnnotations` method into a single `selectAnnotations` method
   with a `toggle` parameter

 - Add tests for `selectAnnotations`

 - Fix an inconsistency where selecting an annotation without holding
   Ctrl to toggle the selection would open the sidebar, but selecting an
   annotation with Ctrl to toggle the selection did not