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/privateOuterFunctions.kt

@@ -0,0 +1,31 @@
+class C {
+    private fun String.ext() : String = ""
+    private fun f() {}
+
+    public fun foo() : String {
+        {
+            "".ext()
+            f()
+        }.invoke()
+
+        object : Runnable {
+            public override fun run() {
+                "".ext()
+                f()
+            }
+        }.run()
+
+        Inner().innerFun()
+
+        return "OK"
+    }
+
+    private inner class Inner() {
+        fun innerFun() {
+            "".ext()
+            f()
+        }
+    }
+}
+
+fun box() = C().foo()