Treat SEALED_SUBCLASS_FQ_NAME_LIST change as a class signature change

#KT-19580

jps-plugin/testData/comparison/classSignatureChange/nestedClassSignatureChanged/new.kt

@@ -0,0 +1,7 @@
+package test
+
+open class Base {
+    class Nested1 {
+        class Nested2
+    }
+}

jps-plugin/testData/comparison/classSignatureChange/nestedClassSignatureChanged/old.kt

@@ -0,0 +1,7 @@
+package test
+
+open class Base {
+    class Nested1 {
+        class Nested2 : Base()
+    }
+}

jps-plugin/testData/comparison/classSignatureChange/nestedClassSignatureChanged/result.out

@@ -0,0 +1,2 @@
+PROTO DIFFERENCE in test/Base.Nested1.Nested2: SUPERTYPE_LIST
+CHANGES in test/Base.Nested1.Nested2: CLASS_SIGNATURE