Remove generated codegen tests, move all testData to box/

A single test file will be generated out of box/ directory

compiler/testData/codegen/box/defaultArguments/constructor/enumWithOneDefArg.kt

@@ -0,0 +1,10 @@
+enum class Foo(val a: Int = 1, val b: String) {
+  B: Foo(2, "b")
+  C: Foo(b = "b")
+}
+
+fun box(): String {
+   if (Foo.B.a != 2 || Foo.B.b != "b") return "fail"
+   if (Foo.C.a != 1 || Foo.C.b != "b") return "fail"
+   return "OK"
+}