Store the getaddrinfo result pointer directly in AddressInfoVector and
free it with freeaddrinfo from the destructor. This keeps the special
cleanup logic local to LibCore instead of relying on OwnPtr custom
deleter support.
By defining this class entirely in the System.h header, we are relying
on ::freeaddrinfo being available. This has led to us polluting the
System.h header with system-level definitions on Windows by way of
SocketAddressWindows.h.