Use actual example code and move safe_fopen to os-test #8344

Job	Run time
mingw (ucrt64)	3m 52s
mingw (mingw64)	3m 42s
build (windows-2022, Win32, v142, 17, Debug)	1m 23s
build (windows-2022, Win32, v142, 17, -DBUILD_SHARED_LIBS=ON, Release)	1m 53s
build (windows-2022, Win32, v142, 17, Release)	2m 8s
build (windows-2022, x64, v142, 17, Release)	2m 35s
build (windows-2022, x64, v142, 20, Debug)	1m 45s
build (windows-2022, x64, v142, 17, -DBUILD_SHARED_LIBS=ON, Debug)	1m 16s
build (windows-2022, x64, v142, 20, Release)	2m 47s
build (windows-2022, x64, v143, Debug, 20)	1m 52s
build (windows-2022, x64, v142, 17, Debug)	1m 10s
build (windows-2022, Win32, v142, 17, -DBUILD_SHARED_LIBS=ON, Debug)	1m 7s
build (windows-2022, x64, v142, 17, -DBUILD_SHARED_LIBS=ON, Release)	2m 18s
	27m 48s

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