* [ios, macos] Introduce MGLPointCollection
This makes MGLMultiPoint abstract again so that it is only a place
for shared functionality of polygons and polylines. The multipoint
feature replaces the point collection feature and can be
used to initialize a MGLGeoJSONSource. The previously added
swift_names for polyline and polygon are removed, for now.
This also updates the iOS and macOS annotation adding logic so that
unwanted shapes really are avoided. Previously the combined OR
conditions meant that an annotation had to logically be NOT a kind
of all three types so the check always let the annotation slip through.
This also expands the guard to deflect the new MGLPointCollection.
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