Annotation views now serve as their own accessibility elements. The developer’s own subclass of MGLAnnotationView can customize the view’s accessibility frame and/or path to more accurately reflect the visual hit target.
Add a container view to hold annotations. This gets around a performance
issue with `UIView:addSubview:` where adding views is N^2. It helps
annotation views avoid cutting into callout views when the annotation
views are transformed to be "flat".