add test for visibility of setter for delegated property (KT-5957)

compiler/testData/writeFlags/delegatedProperty/visibility/privateSet.kt

@@ -0,0 +1,16 @@
+class MyClass() {
+    public var x: Int by Delegate()
+        private set
+}
+
+class Delegate {
+    fun get(t: Any?, p: PropertyMetadata): Int {
+        return 1
+    }
+
+    fun set(t: Any?, p: PropertyMetadata, i: Int) {}
+}
+
+// TESTED_OBJECT_KIND: function
+// TESTED_OBJECTS: MyClass, setX
+// FLAGS: ACC_FINAL, ACC_PRIVATE