chore(tvix/eval): return parse errors out of eval::interpret

Change-Id: I14f25b9c85260c68be38abf07ed80121ead60c7b
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6224
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>
Reviewed-by: grfn <grfn@gws.fyi>

tvix/eval/src/errors.rs

@@ -31,6 +31,8 @@ pub enum Error {
 
     // Unknown variable in dynamic scope (with, rec, ...).
     UnknownDynamicVariable(String),
+
+    ParseErrors(Vec<rnix::parser::ParseError>),
 }
 
 impl Display for Error {