Move blackBoxFile() testData to box/ directory

Delete all test methods (and empty test classes), since they'll be
auto-generated

compiler/testData/codegen/box/classes/kt1120.kt

@@ -0,0 +1,14 @@
+object RefreshQueue {
+    val workerThread: Thread = Thread(object : Runnable {
+        override fun run() {
+            val a = workerThread
+            val b = RefreshQueue.workerThread
+            if (a != b) throw AssertionError()
+        }
+    })
+}
+
+fun box() : String {
+    RefreshQueue.workerThread.run()
+    return "OK"
+}