gh-119396: Optimize unicode_decode_utf8_writer() (#119957) #12

Job	Run time
Interpreter (Debug)	7m 21s
Free-Threaded (Debug)	9m 57s
i686-pc-windows-msvc/msvc (Debug)	19m 52s
i686-pc-windows-msvc/msvc (Release)	22m 28s
x86_64-pc-windows-msvc/msvc (Debug)	18m 26s
x86_64-pc-windows-msvc/msvc (Release)	25m 16s
aarch64-pc-windows-msvc/msvc (Debug)	4m 58s
aarch64-pc-windows-msvc/msvc (Release)	7m 42s
x86_64-apple-darwin/clang (Debug)	13m 33s
x86_64-apple-darwin/clang (Release)	16m 24s
aarch64-apple-darwin/clang (Debug)	11m 15s
aarch64-apple-darwin/clang (Release)	14m 38s
x86_64-unknown-linux-gnu/gcc (Debug)	8m 25s
x86_64-unknown-linux-gnu/gcc (Release)	12m 5s
x86_64-unknown-linux-gnu/clang (Debug)	8m 30s
x86_64-unknown-linux-gnu/clang (Release)	11m 15s
aarch64-unknown-linux-gnu/gcc (Debug)	1h 11m 23s
aarch64-unknown-linux-gnu/gcc (Release)	47m 22s
aarch64-unknown-linux-gnu/clang (Debug)	1h 3m 48s
aarch64-unknown-linux-gnu/clang (Release)	36m 2s
	7h 10m 40s

Provide feedback