Use GoblintCil.upointType directly #13283

Job	Run time
regression (ubuntu-22.04, ocaml-variants.4.14.2+options,ocaml-option-flambda)	8m 8s
gobview (ubuntu-22.04, ocaml-variants.4.14.2+options,ocaml-option-flambda, 14)	7m 8s
regression (macos-13, ocaml-variants.4.14.2+options,ocaml-option-flambda)	19m 43s
extraction	-1s
	34m 58s

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