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/kt247.kt

@@ -0,0 +1,38 @@
+fun t1() : Boolean {
+    val s1 : String? = "sff"
+    val s2 : String? = null
+    return s1?.length == 3 && s2?.length == null
+}
+
+fun t2() : Boolean {
+    val c1: C? = C(1)
+    val c2: C? = null
+    return c1?.x == 1 && c2?.x == null
+}
+
+fun t3() {
+    val d: D = D("s")
+    val x = d?.s
+    if (!(d?.s == "s")) throw AssertionError()
+}
+
+fun t4() {
+    val e: E? = E()
+    if (!(e?.bar() == e)) throw AssertionError()
+    val x = e?.foo()
+}
+
+fun box() : String {
+    if(!t1 ()) return "fail"
+    if(!t2 ()) return "fail"
+    t3()
+    t4()
+    return "OK"
+}
+
+class C(val x: Int)
+class D(val s: String)
+class E() {
+    fun foo() = 1
+    fun bar() = this
+}