Merge pull request #6412 from Eism/playback_toolbar_part2

au4/src/appshell/qml/ProjectPage/ProjectPage.qml

au4/src/au3wrap/CMakeLists.txt

au4/src/au3wrap/au3project.cpp

au4/src/au3wrap/au3project.h

au4/src/au3wrap/au3wrapmodule.cpp

au4/src/au3wrap/au3wrapmodule.h

au4/src/au3wrap/iau3audiooutput.h

au4/src/au3wrap/iau3playback.h

au4/src/au3wrap/internal/au3audiooutput.cpp

au4/src/au3wrap/internal/au3audiooutput.h

au4/src/au3wrap/internal/au3playback.cpp

au4/src/au3wrap/internal/au3playback.h

au4/src/playback/CMakeLists.txt

au4/src/playback/internal/playbackcontroller.cpp

au4/src/playback/internal/playbackcontroller.h

au4/src/playback/internal/playbackuiactions.cpp

au4/src/playback/playback.qrc

au4/src/playback/playbackmodule.cpp

au4/src/playback/qml/Audacity/Playback/PlaybackToolBar.qml

...playback/qml/Audacity/Playback/internal/PlaybackLevel.qml