Add a container view for UIView based annotations

[boundsj]

In #4801 we added the ability for application code to provide UIView based representations for annotations. Currently, the annotation views are added as subviews of the map view. This has potential performance implications and is probably the source if issues like this.

We should add a container view similar to MapKit to contain the annotation views and perhaps other containers for other UIView based visuals. This should help reduce the complexity of layering UIView based visuals over the map.

MapKit annotation container

[boundsj]

@1ec5 @friedbunny I created WIP PR (#5148) for your review.