Nested safe Approve Simulation Feature

[Ethnical]

For now, we don't have a feature to cleanly simulate the approval with the signatures on the nested.just file.
To do that, we need do to an hack into the script (nested.just) to remove the --broadcast and the --legder args but still have a ledger connected.

It would be nice to have a SIMULATE_WITHOUT_LEDGER=1 and simulation feature into the just file to simulate the approval without the ledger.