Release Note: Deprecate the Socket Implementation Factory Mechanism

The following static methods used to set the system-wide socket implementation factories have been deprecated:

 - `static void ServerSocket.setSocketFactory​(SocketImplFactory fac)`
 - `static void Socket.setSocketImplFactory​(SocketImplFactory fac)`
 - `static void DatagramSocket.setDatagramSocketImplFactory​(DatagramSocketImplFactory fac)`

These API points were used to statically configure a system-wide factory for the corresponding socket types in the `java.net` package. These methods have mostly been obsolete since Java 1.4.