test(tvix/eval): enable eval-okay-closure test from nix_tests

This function covers builtins.genericClosure, seemingly including
weird behaviour around the order in which the work set is processed.

For some reason, in C++ Nix the test expectation is written in XML
which we do not yet support, so I have created a new expectation file
using `nix-instantiate --eval --strict` on the file (yes, using C++
Nix).

Change-Id: Id90e7117d120dc66d963a51083c4d8e8f2d9f181
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7311
Reviewed-by: sterni <sternenseemann@systemli.org>
Tested-by: BuildkiteCI

tvix/eval/src/tests/nix_tests/notyetpassing/eval-okay-closure.nix

@@ -1,13 +0,0 @@
-let
-
-  closure = builtins.genericClosure {
-    startSet = [{key = 80;}];
-    operator = {key, foo ? false}:
-      if builtins.lessThan key 0
-      then []
-      else [{key = builtins.sub key 9;} {key = builtins.sub key 13; foo = true;}];
-  };
-
-  sort = (import ./../lib.nix).sortBy (a: b: builtins.lessThan a.key b.key);
-
-in sort closure