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/substitutionInSuperClassDelegation.kt

@@ -0,0 +1,17 @@
+trait A<T> {
+    fun id(t: T): T
+}
+
+open class B : A<String> {
+    override fun id(t: String) = t
+}
+
+class C : B()
+
+class D : A<String> by C()
+
+fun box(): String {
+    val d = D()
+    if (d.id("") != "") return "Fail"
+    return (d : A<String>).id("OK")
+}