v8: backport b3775cf3 from upstream
test: fix http backpressure test case

- use socket timeout event,
- pause socket from the client side.
tls: fix pool usage race

When calling `encOut` in loop, `maybeInitFinished()` may invoke
`clearOut`'s loop, leading to the writing of interleaved data
(encrypted and cleartext) into the one shared pool.

Move `maybeInitFinished()` out of the loop and add assertion for
future.

backport of 60f777d