feat(tvix/eval): Implement comparison for lists

Lists are compared lexicographically in C++ nix as of [0], and our
updated nix test suites depend on this. This implements comparison of
list values in `Value::nix_cmp` using a very similar algorithm to what
C++ does - similarly to there, this requires passing in the VM so we can
force thunks in the list elements as we go.

[0]: 09471d2680#

Change-Id: I5d8bb07f90647a1fec83f775243e21af856afbb1
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7070
Autosubmit: grfn <grfn@gws.fyi>
Reviewed-by: sterni <sternenseemann@systemli.org>
Tested-by: BuildkiteCI

tvix/eval/src/vm.rs

@@ -123,7 +123,7 @@ macro_rules! cmp_op {
     ( $self:ident, $op:tt ) => {{
         let b = $self.pop();
         let a = $self.pop();
-        let ordering = fallible!($self, a.nix_cmp(&b));
+        let ordering = fallible!($self, a.nix_cmp(&b, $self));
         let result = Value::Bool(cmp_op!(@order $op ordering));
         $self.push(result);
     }};