Avoid Re-Adding Resources When Estimate TX At Account.getTransactionCost

[Torres-ssf]

While implementing the getTransactionCost at the Account class on #2643, we forgot to replicate the same logic that it had before when adding fake resources to a TX dry-run execution.

The previous approach involved updating the amounts of existing resources rather than adding new ones.

As a result, this change led to the gasUsed being slightly higher when running getTransactionCost for a transaction that had already been funded.