Generate stubs for private function with default arguments as public in interfaces

compiler/testData/codegen/box/jvm8/defaults/allCompatibility/privateFunWithDefaultArg2.kt

@@ -0,0 +1,22 @@
+// CHECK_BYTECODE_LISTING
+// !JVM_DEFAULT_MODE: all-compatibility
+// TARGET_BACKEND: JVM
+// JVM_TARGET: 1.8
+// WITH_COROUTINES
+// WITH_RUNTIME
+
+interface Foo {
+
+    fun bar(): String {
+        return foo()
+
+    }
+
+    private fun foo(s: String = "OK"): String {
+        return s
+    }
+}
+
+fun box(): String {
+    return object : Foo {}.bar()
+}