Generate more advanced Plutus scripts in `testgen-hs` for the evaluation endpoint

[michalrus]

Context

Follow up to:

• feat: generate transactions, UTxO sets, and execution unit evaluations testgen-hs#2
• feat: generate random transactions for the eval endpoint #340
• Implement tx submit evaluation via pallas & haskell #322

We need to generate more advanced Plutus scripts to really test the endpoint.