[java-completion] JavaNoVariantsDelegator: avoid redundant chains of nested classes

Fixes IDEA-334398 Code completion of nested types suggests confusing levels of nesting

GitOrigin-RevId: 206fc2b9f4a6501720b7bc95e79d981b20450823

java/java-tests/testData/codeInsight/completion/normal/NestedClassCompletion.java

@@ -0,0 +1,13 @@
+sealed interface AddUserError {
+
+  final class NameIsEmpty implements AddUserError {}
+
+  final class NameIsTooLong implements AddUserError {}
+}
+
+class Test {
+
+  public static AddUserError TryAddUser() {
+    return new AUE.<caret>
+  }
+}