util: improve textencoder encodeInto performance #1150

Job	Run time
Build slim tarball	2m 12s
x86_64-linux: with shared libraries	29m 43s
aarch64-linux: with shared libraries	25m 18s
x86_64-darwin: with shared libraries	41m 27s
aarch64-darwin: with shared libraries	30m 36s
	2h 9m 16s

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