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>

corp/tvixbolt/src/main.rs

@@ -286,7 +286,7 @@ fn eval(model: &Model) -> Output {
         return out;
     }
 
-    let mut eval = tvix_eval::Evaluation::new(&model.code, Some("/nixbolt".into()));
+    let mut eval = tvix_eval::Evaluation::default();
     let source = eval.source_map();
 
     let result = {
@@ -298,7 +298,7 @@ fn eval(model: &Model) -> Output {
             eval.runtime_observer = Some(&mut runtime_observer);
         }
 
-        eval.evaluate()
+        eval.evaluate(&model.code, Some("/nixbolt".into()))
     };
 
     if model.display_ast {