stream: preserve toReadableSync batch after backpressure #6725

Job	Run time
Build slim tarball	1m 47s
aarch64-linux: Cache V8 build	22s
aarch64-darwin: with shared libraries	29m 4s
x86_64-linux: with shared libraries	27m 54s
x86_64-darwin: with shared libraries	46m 52s
aarch64-linux: with shared boringssl-0.20260413.0	24m 50s
aarch64-linux: with shared openssl-3.5.5	24m 0s
aarch64-linux: with shared openssl-4.0.0	23m 47s
aarch64-linux: with shared openssl-1.1.1w	22m 28s
aarch64-linux: with shared openssl-3.0.19	24m 11s
aarch64-linux: with shared openssl-3.6.1	23m 8s
	4h 8m 23s

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