optimization of delegates by val property

compiler/testData/codegen/classes/delegationToVal.kt

@@ -0,0 +1,25 @@
+trait IActing {
+  fun act(): String
+}
+
+class CActing(val value: String = "OK"): IActing {
+  override fun act(): String = value
+}
+
+// final so no need in delegate field
+class Test(val acting: CActing = CActing()): IActing by acting {
+}
+
+// even if open so we don't need delegate field
+open class Test2(open val acting: CActing = CActing()): IActing by acting {
+}
+
+// even if open the backing field is final, so we don't need delegate field
+class Test3() : Test2() {
+  override val acting = CActing("OKOK")
+}
+
+fun box(): String {
+  val test = Test()
+  return test.act()
+}