fix issues with moving regions across tracks

inc/audio/automation_region.h

inc/audio/automation_track.h

inc/audio/automation_tracklist.h

inc/audio/track.h

inc/audio/tracklist.h

inc/gui/backend/timeline_selections.h

inc/gui/widgets/arranger.h

inc/gui/widgets/expander_box.h

inc/utils/flags.h

src/actions/arranger_selections.c

src/audio/automation_region.c

src/audio/automation_track.c

src/audio/automation_tracklist.c

src/audio/port.c

src/audio/recording_manager.c

src/audio/tempo_track.c

src/audio/track.c

src/audio/tracklist.c

src/gui/backend/event_manager.c

src/gui/backend/timeline_selections.c