streams: simplify `readableStreamFromIterable` #5223

Job	Run time
Build slim tarball	3m 44s
aarch64-darwin: with shared libraries	22m 17s
x86_64-linux: with shared libraries	24m 24s
aarch64-linux: with shared libraries	19m 45s
x86_64-darwin: with shared libraries	34m 24s
	1h 44m 34s

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