tests/functional2/lang: Move some tests around

Change-Id: I7d87c6c210015b33091876e6656f7c0116bc12ea

tests/functional2/lang/builtins.fetchtree/in-negative.nix

@@ -1,5 +1,5 @@
 builtins.fetchTree {
   type = "file";
-  url = "file://eval-fail-fetchTree-negative.nix";
+  url = "file://in-negative.nix";
   owner = -1;
 }