Merge branch 'drop-down-constructor' into 'master'

GtkDropDown api revisions

See merge request GNOME/gtk!2286

diff --cc demos/gtk-demo/listview_colors.c
Simple merge

diff --cc docs/reference/gtk/gtk4-sections.txt
Simple merge

diff --cc gtk/gtkcustompaperunixdialog.c
Simple merge

diff --cc gtk/gtkdropdown.c
Simple merge

diff --cc gtk/inspector/controllers.c
Simple merge