Simplify foundry-template

[capossele]

• simplify the interaction between app contract and zkVM/Bonsai, by dropping the previously required GuestInterface
• improves testing by leveraging on the ffi cli from risc0-ethereum
• drops the ethereum-sdk as in its current form we think it requires better designing and moves most of its content as a lib of the application's example (i.e., publisher)
• integrates with reproducible builds
• update documentation

TODO:

• Publish risc0-ethereum

[nategraf]

Nice! I want to do a pass on this, trying everything out and providing some edits in a few places. I am going to merge this into capossele/no-relay and do my edit pass there.