fix(ext/net): make unix and tcp identical on close (#13075)
std/http/server knows how to handle "Listener has been closed"
exceptions but not "operation canceled" errors.
Make "unix" listen sockets throw the same exception as "tcp" listen
sockets when the socket is closed and has a pending accept operation.
There is still a discrepancy when multiple accept requests are posted
but that's probably a less visible issue and something for another day.
Fixes #13033
