[ios] Document annotations-as-features limitations w/feature querying

Also move visibleAnnotations next to visibleAnnotationsInRect:.

platform/ios/src/MGLMapView.h

@@ -990,16 +990,6 @@ MGL_EXPORT IB_DESIGNABLE
  */
 @property (nonatomic, readonly, nullable) NS_ARRAY_OF(id <MGLAnnotation>) *annotations;
 
-/**
- The complete list of annotations associated with the receiver that are
- currently visible.
-
- The objects in this array must adopt the `MGLAnnotation` protocol. If no
- annotations are associated with the map view or if no annotations associated
- with the map view are currently visible, the value of this property is `nil`.
- */
-@property (nonatomic, readonly, nullable) NS_ARRAY_OF(id <MGLAnnotation>) *visibleAnnotations;
-
 /**
  Adds an annotation to the map view.
 
@@ -1094,6 +1084,16 @@ MGL_EXPORT IB_DESIGNABLE
  */
 - (nullable __kindof MGLAnnotationView *)dequeueReusableAnnotationViewWithIdentifier:(NSString *)identifier;
 
+/**
+ The complete list of annotations associated with the receiver that are
+ currently visible.
+
+ The objects in this array must adopt the `MGLAnnotation` protocol. If no
+ annotations are associated with the map view or if no annotations associated
+ with the map view are currently visible, the value of this property is `nil`.
+ */
+@property (nonatomic, readonly, nullable) NS_ARRAY_OF(id <MGLAnnotation>) *visibleAnnotations;
+
 /**
  Returns the list of annotations associated with the receiver that intersect with
  the given rectangle.
@@ -1254,6 +1254,11 @@ MGL_EXPORT IB_DESIGNABLE
  `-[MGLVectorSource featuresInSourceLayersWithIdentifiers:predicate:]` and
  `-[MGLShapeSource featuresMatchingPredicate:]` methods on the relevant sources.
 
+ The returned features may also include features corresponding to annotations.
+ These features are not object-equal to the `MGLAnnotation` objects that were
+ originally added to the map. To query the map for annotations, use
+ `visibleAnnotations` or `-[MGLMapView visibleAnnotationsInRect:]`.
+
  @note Layer identifiers are not guaranteed to exist across styles or different
     versions of the same style. Applications that use this API must first set
     the style URL to an explicitly versioned style using a convenience method