Rework unit test report to leverage new reification

And also provide slightly better errors when traces, or trace-if-false operators are present.

crates/uplc/src/machine/eval_result.rs

@@ -1,6 +1,5 @@
-use crate::ast::{Constant, NamedDeBruijn, Term};
-
 use super::{cost_model::ExBudget, Error};
+use crate::ast::{Constant, NamedDeBruijn, Term};
 
 #[derive(Debug)]
 pub struct EvalResult {
@@ -44,6 +43,14 @@ impl EvalResult {
         }
     }
 
+    #[allow(clippy::result_unit_err)]
+    pub fn unwrap_constant(self) -> Result<Constant, ()> {
+        match self.result {
+            Ok(Term::Constant(cst)) => Ok(cst.as_ref().to_owned()),
+            _ => Err(()),
+        }
+    }
+
     pub fn result(&self) -> Result<Term<NamedDeBruijn>, Error> {
         self.result.clone()
     }