feat(tvix/eval): implement builtins.catAttrs

Change-Id: Idf92ac82438fbfcf7b2f6e058830e4744637d8c6
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6262
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>

tvix/eval/src/value/list.rs

@@ -38,4 +38,8 @@ impl NixList {
 
         NixList(stack_slice)
     }
+
+    pub fn into_iter(self) -> std::vec::IntoIter<Value> {
+        self.0.into_iter()
+    }
 }