Fix for KT-7421: Unable to inherit from inner class

Fix for KT-6708: Compiler Error when extending open inner class: "java.lang.RuntimeException: Error generating primary constructor of class InnerB with kind IMPLEMENTATION"

  #KT-7421 Fixed
  #KT-6708 Fixed

compiler/testData/codegen/box/classes/inner/kt6708.kt

@@ -0,0 +1,12 @@
+open class A() {
+    open inner class InnerA
+}
+
+class B : A() {
+    inner class InnerB : A.InnerA()
+}
+
+fun box(): String {
+    B().InnerB()
+    return "OK"
+}

compiler/testData/codegen/box/classes/inner/properSuperLinking.kt

@@ -0,0 +1,16 @@
+
+open class A(val s: String) {
+
+    val z = s
+
+    fun test() = s
+
+    open inner class B(s: String): A(s) {
+        fun testB() = z + test()
+    }
+}
+
+fun box(): String {
+    val res = A("Fail").B("OK").testB()
+    return if (res == "OKOK") "OK" else res;
+}