Treat SEALED_SUBCLASS_FQ_NAME_LIST change as a class signature change

#KT-19580

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

@@ -0,0 +1,12 @@
+package test
+
+sealed class Base1 {
+    class Nested1 : Base1()
+    class Nested2 : Base1()
+}
+
+sealed class Base2 {
+    class Nested1 : Base2()
+    class Nested2 : Base2()
+}
+

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

@@ -0,0 +1,11 @@
+package test
+
+sealed class Base1 {
+    class Nested1 : Base1()
+}
+
+sealed class Base2 {
+    class Nested1 : Base2()
+    class Nested2
+}
+

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

@@ -0,0 +1,8 @@
+ADDED test/Base1.Nested2
+PROTO DIFFERENCE in test/Base1: NESTED_CLASS_NAME_LIST, SEALED_SUBCLASS_FQ_NAME_LIST
+CHANGES in test/Base1: CLASS_SIGNATURE, MEMBERS
+    [Nested2]
+PROTO DIFFERENCE in test/Base2: SEALED_SUBCLASS_FQ_NAME_LIST
+CHANGES in test/Base2: CLASS_SIGNATURE
+PROTO DIFFERENCE in test/Base2.Nested2: SUPERTYPE_LIST
+CHANGES in test/Base2.Nested2: CLASS_SIGNATURE