free all objects immediately (drop `free_later()`)

inc/audio/graph.h

inc/utils/object_utils.h

inc/zrythm.h

src/actions/arranger_selections.c

src/audio/automation_region.c

src/audio/automation_tracklist.c

src/audio/channel.c

src/audio/chord_region.c

src/audio/chord_track.c

src/audio/graph.c

src/audio/marker_track.c

src/audio/midi_region.c

src/audio/modulator_track.c

src/audio/port.c

src/audio/router.c

src/audio/track.c

src/audio/tracklist.c

src/utils/meson.build

src/utils/object_utils.c

src/zrythm.c