basic conversion to C++20 #1549

Job	Run time
Emscripten	3m 24s
FreeBSD	4m 41s
macOS-deps=enabled	1m 23s
macOS-deps=disabled	1m 2s
MSYS	2m 33s
MSYS2-UCRT64-deps=enabled	5m 12s
MSYS2-CLANG64-deps=enabled	3m 22s
Linux-GCC9-deps=forcefallback	8m 31s
MSYS2-UCRT64-deps=disabled	3m 42s
Linux-Clang11-deps=forcefallback	9m 16s
Linux-GCC9-deps=default	1m 37s
MSYS2-CLANG64-deps=disabled	2m 34s
Linux-Clang11-deps=default	1m 40s
Linux-GCC13-deps=forcefallback	9m 7s
Linux-Clang19-deps=forcefallback	9m 43s
Linux-GCC13-deps=default	2m 6s
Linux-Clang19-deps=default	2m 23s
MSVC-forcefallback-x64	5m 0s
clang-cl-forcefallback	5m 43s
clang-cl-default	3m 32s
MSVC-forcefallback-x86	4m 6s
MSVC-default-x64	2m 58s
MSVC-default-x86	3m 5s
	1h 36m 40s

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