'quick' directory renamed to 'tests' which reflects its contents

compiler/testData/diagnostics/tests/Enums.jet

@@ -0,0 +1,10 @@
+enum class List<out T>(val size : Int) {
+  Nil : List<Nothing>(0) {
+    val a = 1
+  }
+  Cons<out T>(val head : T, val tail : List<T>) : List<T>(tail.size + 1)
+
+}
+
+val foo = List.Nil
+val foo1 = foo.a