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/kt633.kt

@@ -0,0 +1,26 @@
+class mInt(val i : Int) {
+    fun toString() : String = "mint: $i"
+    fun plus(i : Int) = mInt(this.i + i)
+    fun inc() = mInt(i + 1)
+}
+
+class MyArray() {
+    val a = Array<mInt>(10, {mInt(0)})
+    fun get(i : mInt) : mInt = a[i.i]
+    fun set(i : mInt, v : mInt) {
+        a[i.i] = v
+    }
+}
+
+fun box() : String {
+    val a = MyArray()
+    var i = mInt(0)
+      System.out?.println(i)
+    a[i++]// = mInt(1)
+      System.out?.println(i)
+    a[i++] = mInt(1)
+      System.out?.println(i)
+    for (i in 0..9)
+      System.out?.println("ar: ${a[mInt(i)]}")
+    return "OK"
+}