util: improve textencoder encodeInto performance #1207

Job	Run time
Build slim tarball	1m 35s
x86_64-darwin: with shared libraries	45m 4s
aarch64-linux: with shared libraries	25m 8s
aarch64-darwin: with shared libraries	27m 23s
x86_64-linux: with shared libraries	29m 35s
	2h 8m 45s

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