Support fmt::runtime with wchar_t in fmt::format_to_n (#4715) #9256

Job	Run time
mingw (ucrt64)	3m 12s
mingw (mingw64)	2m 39s
build (windows-2022, x64, v142, 20, Debug)	1m 32s
build (windows-2022, Win32, v142, 17, -DBUILD_SHARED_LIBS=ON, Release)	1m 58s
build (windows-2022, x64, v142, 17, Release)	2m 13s
build (windows-2022, x64, v142, 17, Debug)	1m 19s
build (windows-2022, Win32, v142, 17, -DBUILD_SHARED_LIBS=ON, Debug)	1m 11s
build (windows-2022, x64, v142, 17, -DBUILD_SHARED_LIBS=ON, Debug)	1m 10s
build (windows-2022, Win32, v142, 17, Release)	2m 5s
build (windows-2022, x64, v142, 17, -DBUILD_SHARED_LIBS=ON, Release)	2m 8s
build (windows-2022, x64, v142, 20, Release)	2m 37s
build (windows-2022, x64, v143, Debug, 20)	1m 35s
build (windows-2022, Win32, v142, 17, Debug)	1m 17s
	24m 56s

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