"Automate" FFmpeg embedding on iOS

1) 6.8.0 added a new cmake function - qt6_add_ios_ffmpeg_libraries - which sets several properties on the target application, resulting in FFmpeg dynamic libraries embedded (and signed) into the application bundle. While this function is documented in the Qt's cmake manual, it requires some changes to pre-existing CMakeLists.txt in an application using QtMultimedia. It makes sense to update Qt's cmake scripts so that such embedding is done 'automatically' without requiring modifications of pre-existing build scripts.
2) qmake-based solutions do not have the functionality mentioned in 1), so manual embedding and setting different flags is still required, worse so, qt-creator does not have UI that allows to embed libraries (though it seems to works well with CMakeLists from 1) ) - either qmake itself or some of its scripts must be updated to enable embedding FFmpeg.