Add execution dry-run just commands

[sebastianst]

We can run a full simulation of a task with just simulate and then, after exporting all sigs to SIGNATURES, execute the task. It'd be great to have an intermediate dry-run command like just dry-run that does everything as close as possible to what execute does, but then doesn't broadcast. So it would use the actual sigs and wouldn't do any nonce or other state overrides etc.

[blmalone]

Referencing this issue: https://github.com/ethereum-optimism/superchain-ops/issues/445 which proposes a solution to the above.