stream: rename `Duplex.toWeb()` type option to `readableType` #3277

Job	Run time
Build slim tarball	3m 6s
x86_64-darwin: with shared libraries	41m 0s
aarch64-linux: with shared libraries	28m 30s
aarch64-darwin: with shared libraries	45m 45s
x86_64-linux: with shared libraries	33m 56s
	2h 32m 17s

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