stream: rename `Duplex.toWeb()` type option to `readableType` #3177

Job	Run time
Build slim tarball	1m 29s
x86_64-darwin: with shared libraries	2h 4m 20s
aarch64-darwin: with shared libraries	1h 49m 14s
aarch64-linux: with shared libraries	59m 23s
x86_64-linux: with shared libraries	1h 29m 47s
	6h 24m 13s

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