Multipoint annotations should be accessible to VoiceOver

[1ec5]

Point annotations are now accessible to VoiceOver, but multipoints (polylines and polygons) are not. Multipoints have no callout views, but it should still be possible to summarize them as, for instance, “{title}, northeast to southwest”.

/cc @friedbunny

[1ec5]

This is blocked on a runtime layer API (#4839), rewriting AnnotationManager based on a style layer inserted at runtime, and feature eventing (#352).

[1ec5]

#352 and #5200 have landed, so this issue is now blocked by #5165.

[stale]

This issue has been automatically detected as stale because it has not had recent activity and will be archived. Thank you for your contributions.