test: stdio pipe behavior tests

Add two regression tests for stdio over pipes.

test-stdio-pipe-access tests if accessing stdio pipe that is being read
by another process does not deadlocks Node.js. This was reported in
https://github.com/nodejs/node/issues/10836 and was fixed in v8.3.0.
The deadlock would happen intermittently, so we run the test 5 times.

test-stdio-pipe-redirect tests if redirecting one child process stdin to
another process stdout does not crash Node as reported in
https://github.com/nodejs/node/issues/17493. It was fixed in
https://github.com/nodejs/node/pull/18019.

PR-URL: https://github.com/nodejs/node/pull/18614


Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>