Add support of enums as dynamic types #3204

Job	Run time
build GTK binaries with gvsbuild	16s
build gtk-rs on Windows (cairo, true, --features png,pdf,svg,ps,use_glib,v1_16,freetype,script,wi...	2m 21s
build gtk-rs on Windows (gdk-pixbuf, true, --features v2_42)	2m 9s
build gtk-rs on Windows (gio, true, --features v2_74)	2m 55s
build gtk-rs on Windows (glib, true, --features v2_74)	4m 37s
build gtk-rs on Windows (glib-build-tools, false)	1m 9s
build gtk-rs on Windows (graphene, false)	2m 16s
build gtk-rs on Windows (pango, true, --features v1_50)	2m 36s
build gtk-rs on Windows (pangocairo, true)	3m 59s
build gtk-rs on Windows (examples, false, --bins --examples --all-features)	3m 26s
	25m 44s

Provide feedback