Auto merge of #23352 - alexcrichton:stabilize-net, r=aturon
This commit performs a stabilization pass over the std::net module,
incorporating the changes from RFC 923. Specifically, the following actions were
taken:
* Extra methods on `Ipv{4,6}Addr` for various methods of inspecting the address
and determining qualities of it.
* Extra methods on `TcpStream` to configure various protocol options.
* Extra methods on `UdpSocket` to configure various protocol options.
Deprecated functionality:
* The `socket_addr` method has been renamed to `local_addr`
This commit is a breaking change due to the restructuring of the `SocketAddr`
type as well as the renaming of the `socket_addr` method. Migration should be
fairly straightforward, however, after accounting for the new level of
abstraction in `SocketAddr` (protocol distinction at the socket address level,
not the IP address).