feat(tvix/eval): Implement OpResolveWith instruction

Change-Id: I4d2a69f28a6b6199b3ff48ef81135e7da9fe1c3b
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6222
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>
Reviewed-by: grfn <grfn@gws.fyi>

tvix/eval/src/errors.rs

@@ -28,6 +28,9 @@ pub enum Error {
 
     // Unknown variable in statically known scope.
     UnknownStaticVariable(rnix::types::Ident),
+
+    // Unknown variable in dynamic scope (with, rec, ...).
+    UnknownDynamicVariable(String),
 }
 
 impl Display for Error {