Cleanup iterator handling #5534

Job	Run time
build (windows-2019, Win32, v142, 17, Debug)	1m 31s
build (windows-2019, Win32, v142, 17, Release)	2m 8s
build (windows-2019, Win32, v142, 17, -DBUILD_SHARED_LIBS=ON, Debug)	1m 57s
mingw (mingw64)	4m 26s
mingw (ucrt64)	4m 33s
build (windows-2019, Win32, v142, 17, -DBUILD_SHARED_LIBS=ON, Release)	2m 25s
build (windows-2019, x64, v140, 14, Debug)	2m 43s
build (windows-2019, x64, v140, 14, Release)	1m 53s
build (windows-2019, x64, v141, 17, Debug)	2m 46s
build (windows-2019, x64, v141, 17, Release)	2m 20s
build (windows-2019, x64, v142, 17, Debug)	2m 0s
build (windows-2019, x64, v142, 17, Release)	2m 17s
build (windows-2019, x64, v142, 17, -DBUILD_SHARED_LIBS=ON, Debug)	1m 25s
build (windows-2019, x64, v142, 17, -DBUILD_SHARED_LIBS=ON, Release)	2m 5s
build (windows-2019, x64, v142, 20, Debug)	1m 24s
build (windows-2019, x64, v142, 20, Release)	2m 39s
build (windows-2022, x64, v143, Debug, 20)	2m 52s
	41m 24s

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