[cryptography] Reduce shared work between Arbiter and Player

[fedemagnani]

When calling .finalize(), the Arbiter performs heavily computations which can be reused by Player during its finalization, if both are running locally (as recommended)

• Computation of Group Polynomial
• Compute weights in case of resharing

Closes #1840

[codecov]

Codecov Report

❌ Patch coverage is 82.30769% with 23 lines in your changes missing coverage. Please review.
✅ Project coverage is 92.09%. Comparing base (27333b9) to head (9d0995d).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
cryptography/src/bls12381/dkg/player.rs	78.09%	23 Missing ⚠️

@@            Coverage Diff             @@
##             main    #1864      +/-   ##
==========================================
- Coverage   92.10%   92.09%   -0.02%     
==========================================
  Files         307      307              
  Lines       79643    79711      +68     
==========================================
+ Hits        73357    73408      +51     
- Misses       6286     6303      +17     

Files with missing lines	Coverage Δ
cryptography/src/bls12381/dkg/arbiter.rs	95.62% <100.00%> (+0.03%)	⬆️
cryptography/src/bls12381/dkg/mod.rs	100.00% <100.00%> (ø)
cryptography/src/bls12381/dkg/ops.rs	95.41% <100.00%> (+0.07%)	⬆️
cryptography/src/bls12381/primitives/poly.rs	98.46% <ø> (ø)
cryptography/src/bls12381/dkg/player.rs	83.25% <78.09%> (-6.89%)	⬇️

... and 1 file with indirect coverage changes

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