action-row: Allow suffixes to expand

GtkBox packs children from the start to end. Unfortunately, here we want to have the opposite so we need to set halign=end on the suffixes box.

However, this also breaks hexpand for its children. There doesn't seem to be a clean way to accomplish it without changing GtkBox, so instead do a little hack: wrap the box into another widget and that would check if the child is expanded and control its halign.