Call IRunListener.featureSkipped for skipped features

FeatureNode.nodeSkipped overrides JUnit 5 platform's Node.nodeSkipped.
It fetches the feature info and then calls IRunListener.featureSkipped
for all run listeners registered on the spec.

Relates to spockframework#1662.

spock-core/src/main/java/org/spockframework/runtime/FeatureNode.java

@@ -47,6 +47,12 @@ public void around(SpockExecutionContext context, Invocation<SpockExecutionConte
     errorInfoCollector.assertEmpty();
   }
 
+  @Override
+  public void nodeSkipped(SpockExecutionContext context, TestDescriptor testDescriptor, SkipResult result) {
+    FeatureInfo featureInfo = getNodeInfo();
+    featureInfo.getSpec().getListeners().forEach(iRunListener -> iRunListener.featureSkipped(featureInfo));
+  }
+
   @Override
   public boolean mayRegisterTests() {
     return getNodeInfo().isParameterized();