Minor, move tests on KT-39054 into a subdirectory

compiler/testData/codegen/box/delegatedProperty/delegateToAnother/custom.kt

@@ -0,0 +1,14 @@
+// WITH_STDLIB
+var x: String
+    get() = throw Exception("x's getter shouldn't be called")
+    set(_) { throw Exception("x's setter shouldn't be called") }
+var y: String by ::x
+
+var storage = "Fail"
+operator fun Any.getValue(thiz: Any?, property: Any?): String = storage
+operator fun Any.setValue(thiz: Any?, property: Any?, value: String) { storage = value }
+
+fun box(): String {
+    y = "OK"
+    return y
+}