chore: Add lurk shard test

[wwared]

Fixes #259

Also addresses the nit from https://github.com/argumentcomputer/loam/pull/260#discussion_r1735229332

This PR does not try to generate a CryptoProof from the MachineProof since the former is in a private module, and exposing it might expose too much as pub we might not want to expose yet. It's extra annoying since tests/fib.rs is technically a separate crate so it couldn't just be pub(crate).

I've manually tested the conversion in the REPL, and indeed when there are multiple shards, all the shards have the same public values and the CryptoProof conversion works fine.

[arthurpaulino]

This single test has increased the test time from 3m to 8m. I believe it's not running the tests in release mode.
Maybe it's worth changing that at this point

[wwared]

@arthurpaulino It's using the dev-ci profile which already has optimizations turned on. It's possible that running the tests in parallel made them slower since all cores are used. I tried changing the nextest config so it won't run the e2e and shard tests in parallel

[wwared]

Looks like it's still really slow in CI (~355s) for some reason, that didn't seem to help :/

For comparison, locally for me this test takes ~135s, which I figured was much more reasonable.

I'll mark this PR as draft for now, since I don't think more than doubling our CI wait times is worth it for this single particular test. Specially considering this test isn't exercising the full CryptoProof/IOProof path either

[arthurpaulino]

For clarity, I'm not exactly against cost increases in our CI. If we need something, we need it.
I mentioned the above just so we make the decision consciously, without letting it slip through our eyes.

[wwared]

Closing for now -- will revisit later