[Scripts] Improve coroutines error handling
[Scripts] Improve coroutines error handling

Specifically, the central selector handles EINTR and the child process
waiter handles ECHILD.

CylonicRaider/Instant,CylonicRaider/Instant,CylonicRaider/Instant,CylonicRaider/Instant,CylonicRaider/Instant