Fix simulation contract deployment during broadcast

[mdehoog]

The Simulation.sol library had some public methods on it, which causes it to be a separate library contract. This means that anything that interacts with Simulation under a broadcast context (e.g. within vm.startBroadcast()) will deploy the Simulation contract.

This PR switches the library methods from public to internal which causes the library to be embedded in the script, which prevents it from being deployed.

It also more narrowly scopes down the broadcast context to only apply to the single safe.execTransaction to prevent this from happening again in future changes.

Also added a feature that skips signatures from non-owning addresses (and warning via console).

[cb-heimdall]

✅ Heimdall Review Status

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