Update gwt rpc span from INTERNAL to SERVER (#7342)

Now that we are allowing/support nested SERVER spans.

cc @lmolkova

Author: trask

instrumentation/gwt-2.0/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/gwt/GwtSingletons.java

@@ -8,6 +8,7 @@
 import io.opentelemetry.api.GlobalOpenTelemetry;
 import io.opentelemetry.context.ContextKey;
 import io.opentelemetry.instrumentation.api.instrumenter.Instrumenter;
+import io.opentelemetry.instrumentation.api.instrumenter.SpanKindExtractor;
 import io.opentelemetry.instrumentation.api.instrumenter.rpc.RpcServerAttributesExtractor;
 import io.opentelemetry.instrumentation.api.instrumenter.rpc.RpcSpanNameExtractor;
 import java.lang.reflect.Method;
@@ -29,9 +30,7 @@ public final class GwtSingletons {
                 INSTRUMENTATION_NAME,
                 RpcSpanNameExtractor.create(rpcAttributesGetter))
             .addAttributesExtractor(RpcServerAttributesExtractor.create(rpcAttributesGetter))
-            // TODO(anuraaga): This should be a server span, but we currently have no way to merge
-            // with the HTTP instrumentation's server span.
-            .buildInstrumenter();
+            .buildInstrumenter(SpanKindExtractor.alwaysServer());
   }
 
   public static Instrumenter<Method, Void> instrumenter() {

instrumentation/gwt-2.0/javaagent/src/test/groovy/GwtTest.groovy

@@ -123,7 +123,7 @@ class GwtTest extends AgentInstrumentationSpecification implements HttpServerTes
         serverSpan(it, 0, getContextPath() + "/greeting/greet")
         span(1) {
           name "test.gwt.shared.MessageService/sendMessage"
-          kind SpanKind.INTERNAL
+          kind SpanKind.SERVER
           childOf(span(0))
           attributes {
             "$SemanticAttributes.RPC_SYSTEM" "gwt"
@@ -147,7 +147,7 @@ class GwtTest extends AgentInstrumentationSpecification implements HttpServerTes
         serverSpan(it, 0, getContextPath() + "/greeting/greet")
         span(1) {
           name "test.gwt.shared.MessageService/sendMessage"
-          kind SpanKind.INTERNAL
+          kind SpanKind.SERVER
           childOf(span(0))
           errorEvent(IOException)
           attributes {