util: improve textencoder encodeInto performance #1311

Job	Run time
Build slim tarball	1m 22s
x86_64-linux: with shared libraries	2h 29m 25s
aarch64-linux: with shared libraries	2h 25m 50s
aarch64-darwin: with shared libraries	2h 0m 4s
x86_64-darwin: with shared libraries	3h 37m 40s
	10h 34m 21s

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