ImageViewer: Transform the image's dimension accordingly to the metadata

Exif metadata have two tags to store the pixel density along each axis.
If both values are different and no action is taken, the resulting image
will appear deformed. This commit scales the displayed bitmap
accordingly to these tags in order to show the image in its intended
shape. This unfortunately includes a lot of plumbing to get this
information through IPC.

Userland/Libraries/LibImageDecoderClient/Client.cpp

@@ -48,6 +48,7 @@ Optional<DecodedImage> Client::decode_image(ReadonlyBytes encoded_data, Optional
     DecodedImage image;
     image.is_animated = response.is_animated();
     image.loop_count = response.loop_count();
+    image.scale = response.scale();
     image.frames.ensure_capacity(response.bitmaps().size());
     auto bitmaps = response.take_bitmaps();
     for (size_t i = 0; i < bitmaps.size(); ++i) {