[ios] Do not allow multipoint annotations to be assigned views

[friedbunny]

Changes

• Limits view annotations to single-point annotations.
• Refactors iosapp’s test shapes into a separate function.
  • Adds detail to the descriptions of individual shapes.
  • Makes the holey shape square (rather than trapezoidal, as below).

Issue

In v3.3.x, it was possible for any annotation class to be assigned an annotation view. If your implementation of -mapView:viewForAnnotation: didn't check if annotation was a kind of MGLPointAnnotation, you could end up drawing view annotations for MGLMultiPoint subclasses, such as MGLPolygon:

As this fix uses the MGLMultiPoint superclass to exclude polygons and polylines, we will have to reevaluate if/when the proposed geometry class hierarchy changes in #5201 happen.

/cc @boundsj @1ec5 @incanus @frederoni

[1ec5]

👍