getEvals: order by the eval table's ID

I broke this when I added `me.` in f1e75c8bffec3f5f86122ee73e3c0f19e26ddb27

I added me. to disambiguate `id`, but:

* eval.id works on the per-build page
* me.id works on the other pages
* Just id works everywhere if I drop:

    , prefetch => { evaluationerror => [ ] },

  but this causes a query per row to collect the evaluationerror
  records later, this becomes significantly slow on non-trivial
  datasets.

Using evals->current_source_alias will use the correct alias
whether it is me or eval or something else.

src/lib/Hydra/Helper/Nix.pm

@@ -226,9 +226,11 @@ sub getEvalInfo {
 sub getEvals {
     my ($self, $c, $evals, $offset, $rows) = @_;
 
+    my $me = $evals->current_source_alias;
+
     my @evals = $evals->search(
         { hasnewbuilds => 1 },
-        { order_by => "me.id DESC", rows => $rows, offset => $offset
+        { order_by => "$me.id DESC", rows => $rows, offset => $offset
         , prefetch => { evaluationerror => [ ] } });
     my @res = ();
     my $cache = {};