Align output of tx simulate with other Aiken's commands.

And also return a structured output as JSON, so it's more easily used
  by other tools.

  ```
       Parsing script context
    Simulating 78ec148ea647cf9969446891af31939c5d57b275a2455706782c6183ef0b62f1
      Redeemer Spend → 0

  {"mem":151993,"cpu":58180696}
  ```

crates/uplc/src/machine/cost_model.rs

@@ -18,7 +18,7 @@ macro_rules! hashmap {
 }
 
 /// Can be negative
-#[derive(Debug, Clone, PartialEq, Eq, Copy)]
+#[derive(Debug, Clone, PartialEq, Eq, Copy, serde::Serialize)]
 pub struct ExBudget {
     pub mem: i64,
     pub cpu: i64,