Simulate: Support "extra-fees" field for simulating the group with additional fees

## Problem

To properly use simulate the caller must ensure that all of the outer fees are enough to make the evaluation succeed. This can be problematic for transaction groups with multiple transactions because it's not always obvious which sender/txn should increase its fee for simulation. It is also not always obvious how much that fee should be and whether or not the sender can actually pay that amount.

## Solution

Add an `extra-fees` (or similarly named) parameter to simulate that adds a specified amount to the total outer group fee without actually charging any of the senders or attaching it to a specific transaction.

## Dependencies

None

## Urgency

Medium - For now apps can use heuristics to know how much fees to add and to which accounts, but having this feature will make it much easier to use simulate for fee information

Start by locating the simulate entry point and the existing outer-group fee handling in go-algorand. Trace how simulation inputs are validated and how fees affect evaluation, then add focused coverage for the new extra-fees parameter. Done means the specified amount contributes to the simulated group fee without charging a sender or attaching it to an individual transaction.

Scritto dal modello di indicizzazione a partire dal testo della issue.