refactor(tvix/eval): remove code and location from struct

Instead, it's passed in the evaluate/compile_only functions, which feels
more naturally. It lets us set up the Evaluation struct long before
we actually feed it with data to evaluate.

Now that Evaluation::new() would be accepting an empty list of
arguments, we can simply implement Default, making things a bit more
idiomatic.

Change-Id: I4369658634909a0c504fdffa18242a130daa0239
Reviewed-on: https://cl.tvl.fyi/c/depot/+/10475
Tested-by: BuildkiteCI
Reviewed-by: tazjin <tazjin@tvl.su>
Autosubmit: flokli <flokli@flokli.de>

tvix/glue/src/tvix_store_io.rs

@@ -375,7 +375,7 @@ mod tests {
     /// Takes care of setting up the evaluator so it knows about the
     // `derivation` builtin.
     fn eval(str: &str) -> EvaluationResult {
-        let mut eval = tvix_eval::Evaluation::new_impure(str, None);
+        let mut eval = tvix_eval::Evaluation::new_impure();
 
         let blob_service = Arc::new(MemoryBlobService::default());
         let directory_service = Arc::new(MemoryDirectoryService::default());
@@ -397,7 +397,7 @@ mod tests {
         add_derivation_builtins(&mut eval, known_paths.clone());
 
         // run the evaluation itself.
-        eval.evaluate()
+        eval.evaluate(str, None)
     }
 
     /// Helper function that takes a &Path, and invokes a tvix evaluator coercing that path to a string