Implementation of CryptographicSponge for Merlin

[autquis]

Using Merlin, we have the possibility of having a sponge that is not generic on a field.

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[mmagician]

@hdevalence

[autquis]

I had to remove the redundant imports since cargo +nightly check complained. Specifically, Vec is in the prelude and is redundant to import.

[mmagician]

@autquis ah yes see also this PR: arkworks-rs/algebra#790 to tackle the same sort of issues in algebra

Edit: I actually wonder why this works, given that similar changes in poly commit failed no-std

[autquis]

@mmagician I didn't understand what I should fix in arkworks-rs/algebra#790? As it is merged already.

Why it works: I guess because it is not completely no-default-features and r1cs is enabled. This is the command for no_std check:

cargo build --no-default-features --features=r1cs --target aarch64-unknown-none

[mmagician]

What I meant is that the algebra PR addressed similar issues.

[autquis]

A gentle ping :)

[mmagician]

Also @mmaker since I'm tagging you in a few places now, maybe you could also take a peek at this?

[autquis]

CI failure is due to this change probably rust-lang/rust#121752
@Cesar199999 @Antonio95

[Cesar199999]

@autquis Yes sorry, I had to update the branch, I'll fix it

[mmaker]

Took a quick peek! The PR looks okay, but there isn't much to say. I'd personally encourage your to add a few lines of documentation so that people are well-aware of the limitations of this trait, especially concerning the statement serialization (the user is on their own) and the bit vs bytes part.

That said, I'm happy to see that people are starting to need something that works both over bytes and algebraic sponges :)