gtk.cfg: Add G_DEPRECATED_FOR and G_ENCODE_VERSION (#8708) #20325

Job	Run time
build_make (ubuntu:25.10)	5m 19s
build_cmake (ubuntu:25.10, true, true)	5m 58s
build_cmake (alpine:3.23, false, false)	4m 40s
build_cmake (ubuntu:24.04, true, true)	5m 33s
build_make (ubuntu:24.04)	4m 16s
build_make (alpine:3.23)	6m 19s
	32m 5s

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