[core][ios][osx][android] make SpriteImage accept PremultipliedImage

the SpriteImage constructor signature changes from

SpriteImage(
        uint16_t width, uint16_t height, float pixelRatio,
        std::string&& data, bool sdf = false);

to

SpriteImage(PremultipliedImage&&, float pixelRatio, bool sdf = false)

test/api/annotations.cpp

@@ -16,7 +16,7 @@ using namespace mbgl;
 
 std::shared_ptr<SpriteImage> namedMarker(const std::string &name) {
     PremultipliedImage image = decodeImage(util::read_file("test/fixtures/sprites/" + name));
-    return std::make_shared<SpriteImage>(image.width, image.height, 1.0, std::string(reinterpret_cast<char*>(image.data.get()), image.size()));
+    return std::make_shared<SpriteImage>(std::move(image), 1.0);
 }
 
 namespace {