Currently when using uasyncio.start_server() the socket configuration is
done inside a uasyncio.create_task() background function. If the address
and port are already in use however this throws an OSError which cannot be
cleanly caught behind the create_task().
This commit moves the getaddrinfo and socket binding to the start_server()
function, and only creates the task if that succeeds. This means that any
OSError from the initial socket configuration is propagated directly up the
call stack, compatible with CPython behaviour.
See #7444.
Signed-off-by: Damien George <damien@micropython.org>
