added one more test to check if overrides are resolved correctly

compiler/testData/diagnostics/tests/Delegation_Hierarchy.kt

@@ -0,0 +1,12 @@
+trait A {
+    fun foo() {}
+}
+
+open class B(a: A) : A by a
+
+class C(a: A): B(a), A {
+}
+
+fun b(c: C) {
+    c.foo();
+}