Refactor Governance example to use the new foundry template

[capossele]

• Should move the Governance example from risc0/ repo to risc0/ethereum
• Should close Update OpenZeppelin dependencies #7 alongside this one.
• Update doc links to the new repository risc0-ethereum

[capossele]

With risc0/risc0#1525 we want to drop all ethereum related crates from risc0. We should move the current version of the governance or un updated one on this repo, and adjust the links on the risc0 website to point on this repo

Unfortunately we don't have effective link checkers to help manage 404 errors, but these places come to mind as likely to have links to the ethereum demos.

the use cases page
the examples page
blogs -- on governance and on coprocessors (sherry or vee can support on getting links in these fixed)

[Cardosaum]

Blocked on issues with remappings.txt