Issue #3106 - deprecate old WebSocket stats mechanism

Signed-off-by: Lachlan Roberts <lachlan@webtide.com>

jetty-websocket/websocket-common/src/main/java/org/eclipse/jetty/websocket/common/io/AbstractWebSocketConnection.java

@@ -101,6 +101,7 @@ public abstract class AbstractWebSocketConnection extends AbstractConnection imp
         }
     }
 
+    @Deprecated
     public static class Stats
     {
         private AtomicLong countFillInterestedEvents = new AtomicLong(0);
@@ -402,6 +403,7 @@ public abstract class AbstractWebSocketConnection extends AbstractConnection imp
         return scheduler;
     }
 
+    @Deprecated()
     public Stats getStats()
     {
         return stats;