add ultra-light classes/members that work without backend in simple cases

compiler/testData/asJava/ultraLightClasses/delegatingToInterfaces.kt

@@ -0,0 +1,15 @@
+
+interface Base {
+    fun printMessage()
+    fun printMessageLine()
+}
+
+class BaseImpl(val x: Int) : Base {
+    override fun printMessage() { print(x) }
+    override fun printMessageLine() { println(x) }
+}
+
+/** should load cls */
+class Derived(b: Base) : Base by b {
+    override fun printMessage() { print("abc") }
+}