Use actual example code and move safe_fopen to os-test #8345

Job	Run time
mingw (ucrt64)	3m 49s
mingw (mingw64)	3m 51s
build (windows-2022, Win32, v142, 17, Debug)	1m 12s
build (windows-2022, Win32, v142, 17, -DBUILD_SHARED_LIBS=ON, Release)	1m 54s
build (windows-2022, x64, v142, 17, -DBUILD_SHARED_LIBS=ON, Debug)	1m 10s
build (windows-2022, x64, v142, 20, Release)	2m 40s
build (windows-2022, Win32, v142, 17, Release)	2m 0s
build (windows-2022, Win32, v142, 17, -DBUILD_SHARED_LIBS=ON, Debug)	1m 6s
build (windows-2022, x64, v142, 17, Debug)	1m 15s
build (windows-2022, x64, v142, 17, -DBUILD_SHARED_LIBS=ON, Release)	2m 8s
build (windows-2022, x64, v142, 17, Release)	2m 17s
build (windows-2022, x64, v143, Debug, 20)	2m 29s
build (windows-2022, x64, v142, 20, Debug)	2m 11s
	28m 2s

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