Stark: Implement Stone compatible grinding

[schouhy]

Implement Stone compatible grinding

Description

This PR implements the grinding strategy of Stone prover. That means, a nonce is valid if hash(hash(prefix || seed || grinding_factor) || nonce) has at least grinding_factor leading zeros. Where prefix is 0x0123456789abcded and seed is the state of the transcript (References: here and here)

The values of the tests were extacted from running Stone prover case 1 with the different grinding factors.

Type of change

Please delete options that are not relevant.

• New feature

Checklist

• Unit tests added
• This change requires new documentation.
  • Documentation has been added/updated.

[codecov-commenter]

Codecov Report

Merging #616 (db0616d) into main (f940e14) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main     #616   +/-   ##
=======================================
  Coverage   97.11%   97.12%           
=======================================
  Files         114      114           
  Lines       26540    26599   +59     
=======================================
+ Hits        25775    25834   +59     
  Misses        765      765           

Files	Coverage Δ
provers/stark/src/grinding.rs	100.00% <100.00%> (ø)
provers/stark/src/prover.rs	99.91% <100.00%> (-0.01%)	⬇️
provers/stark/src/verifier.rs	99.38% <100.00%> (-0.01%)	⬇️

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