Finish last remaining refactor LibauthTemplate.ts

Finish last remaining refactor of `LibauthTemplate.ts` logic, we have a TODO in the code for this:

```ts
export const getLibauthTemplate = (
  transactionBuilder: TransactionBuilder,
): WalletTemplate => {
  ....

  // TODO: Refactor the below code to not have deep reassignment of scenario.sourceOutputs and scenario.transaction.outputs
```