Server has some extensions checking for inputMediaUploadedPhoto,
so force the extension to be .jpg anyway. It doesn't matter,
because the filename from inputFile is not used anywhere.
Also own PhotoData::UploadingData through std::unique_ptr.
Read media information (image / song / video) in SendFileBox in the
same way it is read in FileLoadTask::process() and reuse it in
FileLoadTask if it was loaded already for the box.
