properties-window: Use property rows in "create_extension_group_row"
AdwActionRows and AdwExpanderRows can become property rows by adding the .property style class[1]. This achieves the same behavior that create_extension_group_row currently has, but with less code.
Related: #3183 (closed)
[1] https://gnome.pages.gitlab.gnome.org/libadwaita/doc/main/style-classes.html#property-rows