Ensure AnnotationManager's mapLoaded happens first

[macdrevx]

Pull request checklist:

• Briefly describe the changes in this PR.
• Write tests for all new functionality. If tests were not written, please explain why.
  • This does not test that Annotation manager is created during MapView initialization. If that were to change, this could break again. Testing it would require significant refactoring that is beyond the scope of this fix.
• Document any changes to public APIs.
• Apply changelog label ('breaking change', 'bug 🪲', 'build', 'docs', 'feature 🍏', 'performance ⚡', 'testing 💯') or use the label 'skip changelog'
• Add an entry inside this element for inclusion in the mapbox-maps-ios changelog: <changelog></changelog>. Added directly to changelog in PR
• Update the migration guide, API Docs, Markdown files - Readme, Developing, etc

Summary of changes

Previously, AnnotationManager subscribed to .mapLoaded using
MapboxCoreMaps directly; however, MapboxCoreMaps does not guarantee
that observers will be notified in the order in which they subscribe.

Among other things, this could result in annotations not being selected when they are tapped.

This fix updates AnnotationManager to subscribe via BaseMapView.on
which does guarantee notification ordering among its subscribers.

Breaking changes:

• AnnotationManager no longer conforms to Observer and no longer has a peer
• AnnotationSupportableMap is now internal