inline superclass refactoring: allow to collapse only one inheritance (IDEA-93319)

java/java-tests/testData/refactoring/inlineSuperClass/inlineOneClass/after/Super.java

@@ -0,0 +1,3 @@
+abstract class Super {
+   public abstract void method() {}
+}

java/java-tests/testData/refactoring/inlineSuperClass/inlineOneClass/after/Test.java

@@ -0,0 +1,16 @@
+class Test {
+  public void context() {
+    method();
+  }
+
+  public void method() {}
+}
+
+class Test1 extends Super {
+   @Override
+   public void method() {}
+}
+
+class U {
+  Super t = new Test1();
+}