Fix format_to + FMT_STRING for wide character type #6007

Job	Run time
mingw (mingw64)	3m 39s
mingw (ucrt64)	4m 13s
build (windows-2019, Win32, v142, 17, Debug)	2m 13s
build (windows-2019, Win32, v142, 17, Release)	2m 59s
build (windows-2019, Win32, v142, 17, -DBUILD_SHARED_LIBS=ON, Debug)	1m 24s
build (windows-2019, Win32, v142, 17, -DBUILD_SHARED_LIBS=ON, Release)	2m 50s
build (windows-2019, x64, v140, 14, Debug)	2m 6s
build (windows-2019, x64, v140, 14, Release)	2m 21s
build (windows-2019, x64, v141, 17, Debug)	1m 56s
build (windows-2019, x64, v141, 17, Release)	3m 4s
build (windows-2019, x64, v142, 17, Debug)	1m 25s
build (windows-2019, x64, v142, 17, Release)	2m 19s
build (windows-2019, x64, v142, 17, -DBUILD_SHARED_LIBS=ON, Debug)	1m 58s
build (windows-2019, x64, v142, 17, -DBUILD_SHARED_LIBS=ON, Release)	2m 37s
build (windows-2019, x64, v142, 20, Debug)	1m 35s
build (windows-2019, x64, v142, 20, Release)	3m 4s
build (windows-2022, x64, v143, Debug, 20)	1m 44s
	41m 27s

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