Merge boxMultiFile testData into box, delete BoxMultiFile test

compiler/testData/codegen/box/syntheticAccessors/kt10047.kt

@@ -0,0 +1,36 @@
+// FILE: a.kt
+
+package test2
+
+import test.Actor
+import test.O2dScriptAction
+
+class CompositeActor : Actor()
+
+public open class O2dDialog : O2dScriptAction<CompositeActor>() {
+
+    fun test() = { owner }()
+
+    fun test2() = { calc() }()
+}
+
+fun box(): String {
+    if (O2dDialog().test() != null) return "fail 1"
+    if (O2dDialog().test2() != null) return "fail 2"
+
+    return "OK"
+}
+
+// FILE: b.kt
+
+package test
+
+open class Actor
+
+abstract public class O2dScriptAction<T : Actor> {
+    protected var owner: T? = null
+        private set
+
+    protected fun calc(): T? = null
+
+}