util: improve textencoder encodeInto performance #1133

Job	Run time
Build slim tarball	1m 30s
x86_64-linux: with shared libraries	2m 34s
aarch64-darwin: with shared libraries	2m 41s
x86_64-darwin: with shared libraries	2m 41s
aarch64-linux: with shared libraries	2m 33s
	11m 59s

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