[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/fixtures/util.cpp

@@ -89,6 +89,7 @@ Server::~Server() {
     }
 }
 
+
 // from https://gist.github.com/ArtemGr/997887
 uint64_t crc64(const char* data, size_t size) {
     boost::crc_optimal<64, 0x04C11DB7, 0, 0, false, false> crc;
@@ -100,6 +101,10 @@ uint64_t crc64(const std::string& str) {
     return crc64(str.data(), str.size());
 }
 
+uint64_t crc64(const PremultipliedImage &image) {
+    return crc64(reinterpret_cast<const char*>(image.data.get()), image.size());
+}
+
 PremultipliedImage render(Map& map, std::chrono::milliseconds timeout) {
     std::promise<PremultipliedImage> promise;
     map.renderStill([&](std::exception_ptr, PremultipliedImage&& image) {