Deprecate zpages from opentelemetry-sdk-extension-incubator (#5578)

sdk-extensions/incubator/src/main/java/io/opentelemetry/sdk/extension/incubator/trace/zpages/ZPageServer.java

@@ -68,8 +68,13 @@ import javax.annotation.concurrent.ThreadSafe;
  *   }
  * }
  * }</pre>
+ *
+ * @deprecated for removal without replacement. See <a
+ *     href="https://github.com/open-telemetry/opentelemetry-java/issues/5571">opentelemetry-java#5571</a>
+ *     for details.
  */
 @ThreadSafe
+@Deprecated
 public final class ZPageServer {
   // The maximum number of queued incoming connections allowed on the HttpServer listening socket.
   private static final int HTTPSERVER_BACKLOG = 5;

sdk-extensions/incubator/src/test/java/io/opentelemetry/sdk/extension/incubator/trace/zpages/ZPageServerTest.java

@@ -11,6 +11,7 @@ import io.opentelemetry.sdk.trace.SdkTracerProvider;
 import io.opentelemetry.sdk.trace.SpanLimits;
 import org.junit.jupiter.api.Test;
 
+@SuppressWarnings("deprecation") // Testing deprecated code
 class ZPageServerTest {
 
   @Test