Change Debug impl of SocketAddr and IpAddr to match their Display output

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.

library/std/src/net/addr.rs

@@ -37,7 +37,7 @@
 /// assert_eq!(socket.port(), 8080);
 /// assert_eq!(socket.is_ipv4(), true);
 /// ```
-#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, PartialOrd, Ord)]
+#[derive(Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord)]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub enum SocketAddr {
     /// An IPv4 socket address.
@@ -597,6 +597,13 @@ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
     }
 }
 
+#[stable(feature = "rust1", since = "1.0.0")]
+impl fmt::Debug for SocketAddr {
+    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+        fmt::Display::fmt(self, fmt)
+    }
+}
+
 #[stable(feature = "rust1", since = "1.0.0")]
 impl fmt::Display for SocketAddrV4 {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {

library/std/src/net/ip.rs

@@ -39,7 +39,7 @@
 /// assert_eq!(localhost_v4.is_ipv4(), true);
 /// ```
 #[stable(feature = "ip_addr", since = "1.7.0")]
-#[derive(Copy, Clone, Eq, PartialEq, Debug, Hash, PartialOrd, Ord)]
+#[derive(Copy, Clone, Eq, PartialEq, Hash, PartialOrd, Ord)]
 pub enum IpAddr {
     /// An IPv4 address.
     #[stable(feature = "ip_addr", since = "1.7.0")]
@@ -811,6 +811,13 @@ fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
     }
 }
 
+#[stable(feature = "ip_addr", since = "1.7.0")]
+impl fmt::Debug for IpAddr {
+    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+        fmt::Display::fmt(self, fmt)
+    }
+}
+
 #[stable(feature = "ip_from_ip", since = "1.16.0")]
 impl From<Ipv4Addr> for IpAddr {
     /// Copies this address to a new `IpAddr::V4`.