fix(ext/node): only set our end of child process pipe to nonblocking mode (#26495)
Fixes playwright on linux, as reported in
https://github.com/denoland/deno/issues/16899#issuecomment-2378268454.
The issue was that we were opening the socket in nonblocking mode, which
meant that subprocesses trying to use it would get a `EWOULDBLOCK` error
(unexpectedly). The fix here is to only set nonblocking mode on our end
(which we need to use asynchronously)