Commit multiple columns using a single Merkle Tree

[schouhy]

This PR adds the following:

1. Use a modified version of Merkle trees that don't hash back to Field Elements and builds the entire tree using bytes.
2. Instead of building a Merkle tree for each column of the RAP, use a single Merkle tree for the trace columns of the main part of the RAP another Merkle tree for the second part. The data of each leaf of these merkle trees are the vectors of evaluations of all the polynomials involved.

There are two merkle trees for each part of the RAP because the prover needs to commit to the first ones before getting the RAP challenges from the verifier. Improvements on this are left for another PR.

Benchmarking CAIRO/fibonacci/10: Collecting 10 samples in estimated 31.762 s (99
CAIRO/fibonacci/10      time:   [31.787 ms 32.771 ms 34.208 ms]
                        change: [-42.359% -40.011% -37.434%] (p = 0.00 < 0.05)
                        Performance has improved.
Benchmarking CAIRO/fibonacci/30: Collecting 10 samples in estimated 32.952 s (44
CAIRO/fibonacci/30      time:   [67.688 ms 68.215 ms 69.366 ms]
                        change: [-38.890% -36.275% -33.590%] (p = 0.00 < 0.05)
                        Performance has improved.

[codecov-commenter]

Codecov Report

Merging #47 (2556a4a) into main (7f0178e) will increase coverage by 0.18%.
The diff coverage is 99.54%.

@@            Coverage Diff             @@
##             main      #47      +/-   ##
==========================================
+ Coverage   97.84%   98.02%   +0.18%     
==========================================
  Files          33       33              
  Lines        4956     5075     +119     
==========================================
+ Hits         4849     4975     +126     
+ Misses        107      100       -7     

Impacted Files	Coverage Δ
src/fri/fri_decommit.rs	0.00% <ø> (ø)
src/proof.rs	0.00% <ø> (ø)
src/lib.rs	98.94% <99.24%> (+0.50%)	⬆️
src/fri/fri_commitment.rs	100.00% <100.00%> (ø)
src/fri/mod.rs	98.85% <100.00%> (ø)
src/prover.rs	99.83% <100.00%> (-0.01%)	⬇️
src/verifier.rs	99.25% <100.00%> (-0.02%)	⬇️

... and 1 file with indirect coverage changes

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