Remove hardcoded addresses

[mds1]

Tasks often have hardcoded addresses, such as in the .env files. These are hard to verify, as the task reviewers need to find a source of truth for validating an address.

Instead, for commonly used addresses that are not in the superchain registry, we should:

• First try to add them to the superchain registry. May need to work with @bitwiseguy @geoknee @alfonso-op on this
• If for some reason we don't want them in the Superchain Registry, consider an addresses.toml file for each network (i.e. one in tasks/eth, one in tasks/sep, etc. Consider an approach like the JSON address files used in forge-proposal-simulator which are parsed via their Addresses.sol file.

Then, the justfiles and solidity scripts should read addresses from those two sources.

The .env file often needs to define the safe that is signing—this can instead be a role or Safe name, and converted from a name to an address based on the above sources.

This issue should only be done after #335 to provide confidence that the changes work as intended. We should ensure that the changes made by this issue are covered by the test tasks added by #335, and if not, expand the scope of the test tasks to ensure converage