test: raise sleep times in child process tests
sequential/test-child-process-execsync and parallel/test-child-process-spawnsync-timeout are both flaky on azure Windows machines, where it may take longer for Node.js to launch and receive output from child processes. These tests work by spawning a child processes that is supposed to sleep for a long time, but the option is configured so that Node.js would terminate them early when a shorter timeout is reached. Then the tests assert that the time taken for the whole thing is shorter than the specified sleep time (meaning the process don't actually get to sleep for that long). To make the tests less brittle on azure Windows, this patch raises the sleep times in those tests on Windows platform, so that the overhead can be taken into account there.