This has already been done for `SocketAddrV4`, `SocketAddrV6`,
`IpAddrV4` and `IpAddrV6`. I don't see a point to keep the rather bad
to read derived impl, especially when pretty printing:
V4(
127.0.0.1
)
From the `Display`, one can easily and unambiguously see if it's V4 or
V6. Using `Display` as `Debug` is very convenient for configuration
structs (e.g. for webservers) that often just have a `derive(Debug)`
and are printed that way to the user.
