Move blackBoxFile() testData to box/ directory

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

compiler/testData/codegen/box/safeCall/kt232.kt

@@ -0,0 +1,10 @@
+class A() {
+    fun foo() {
+        System.out?.println(1)
+    }
+}
+
+fun box() : String {
+    val a : A = A()
+    return "OK"
+}