lib/addr.c, etc.: Return plain addresses from `netaddress_resolve'.

lib/addr.c, etc.: Return plain addresses from `netaddress_resolve'.

Instead of a list of `struct addrinfo' structures, return a vector of
`struct resolved', each of which just contains a socket address and
length.  This is sufficient for all of the existing callers (which have
been changed to cope), and means that we don't need any awful hacks
because they're easy to free.