Move blackBoxFile() testData to box/ directory

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

compiler/testData/codegen/box/bridges/diamond.kt

@@ -0,0 +1,23 @@
+trait A<T, U> {
+    fun foo(t: T, u: U) = "A"
+}
+
+trait B<U> : A<String, U>
+
+trait C<T> : A<T, Int>
+
+class Z : B<Int>, C<String> {
+    override fun foo(t: String, u: Int) = "Z"
+}
+
+
+fun box(): String {
+    val z = Z()
+    return when {
+        z.foo("", 0)                    != "Z" -> "Fail #1"
+        (z : C<String>).foo("", 0)      != "Z" -> "Fail #2"
+        (z : B<Int>).foo("", 0)         != "Z" -> "Fail #3"
+        (z : A<String, Int>).foo("", 0) != "Z" -> "Fail #4"
+        else -> "OK"
+    }
+}