Returns an array of IP address strings, formatted according to RFC 5952,
that are currently configured for DNS resolution. A string will include a port
section if a custom port is used.
[
'4.4.4.4',
'2001:4860:4860::8888',
'4.4.4.4:1053',
'[2001:4860:4860::8888]:1053',
]