test(tvix/eval): Add Eq-laws tests for NixAttrs

As before, this limits the cases to a relatively small number because
otherwise things get quite large.

Change-Id: I5371dc56418fca52e1dd1d905b20868f647091ba
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6649
Autosubmit: grfn <grfn@gws.fyi>
Tested-by: BuildkiteCI
Reviewed-by: tazjin <tazjin@tvl.su>

tvix/eval/src/value/attrs/tests.rs

@@ -1,4 +1,15 @@
+use proptest::prelude::ProptestConfig;
+
 use super::*;
+use crate::properties::eq_laws;
+
+eq_laws!(
+    NixAttrs,
+    ProptestConfig {
+        cases: 5,
+        ..Default::default()
+    }
+);
 
 #[test]
 fn test_empty_attrs() {