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/kt1959.kt

@@ -0,0 +1,13 @@
+open class A<T> {
+    open fun f(args : Array<T>) {}
+}
+
+class B(): A<String>() {
+    override fun f(args : Array<String>) {}
+}
+
+fun main(args: Array<String>) {
+    B()
+}
+
+fun box(): String = "OK"