Merge boxMultiFile testData into box, delete BoxMultiFile test

compiler/testData/codegen/box/sam/constructors/samWrappersDifferentFiles.kt

@@ -0,0 +1,23 @@
+// WITH_RUNTIME
+// FILE: 1/wrapped.kt
+
+fun getWrapped1(): Runnable {
+    val f = { }
+    return Runnable(f)
+}
+
+// FILE: 2/wrapped2.kt
+
+fun getWrapped2(): Runnable {
+    val f = { }
+    return Runnable(f)
+}
+
+// FILE: box.kt
+
+fun box(): String {
+    val class1 = getWrapped1().javaClass
+    val class2 = getWrapped2().javaClass
+
+    return if (class1 != class2) "OK" else "Same class: $class1"
+}