Make Yul proto mutator mutations deterministic.

[bshastry]

The Yul proto mutator is a set of libprotobuf-mutator callbacks that mutates Yul protobuf inputs using custom mutations e.g., add a store here, flip a bool there etc.

The mutator itself would statically initialize a random number generator to eventually produce mutations. However, this would mean that depending on how many times the mutator has been called, the mutation would differ. Meaning that when debugging a crash, it may no longer reproduce because the statically initialized RNG would not cause a mutation or cause a different one.

This PR fixes this non-determinism by making use of (deterministic) seeds provided by the libprotobuf mutator library. Now, crashes should be reproducible outside fuzzing runs.

[cameel]

Does not look like it could break things so approving.

Hopefully it does improve the situation, though it's hard to judge just by looking at the PR itself. Should we see the effect in one of our CI jobs?

[bshastry]

Does not look like it could break things so approving.

Hopefully it does improve the situation, though it's hard to judge just by looking at the PR itself. Should we see the effect in one of our CI jobs?

Sadly not, since we don't have tests for the custom mutator. Adding tests has weighed on my mind before but I've not acted on it, may be I should prioritize it.