Add BN254 Curve for Groth16

[nicole-graus]

Add BN254 Curve for Groth16 Prover

Description

This PR allows the use of the curve BN254 to prove and verify proofs using Groth16. It also reorganize the prover's folder to include both curves.

Type of change

Please delete options that are not relevant.

• New feature

Checklist

• Linked to Github Issue
• Unit tests added
• This change requires new documentation.
  • Documentation has been added/updated.
• This change is an Optimization
  • Benchmarks added/run

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 88.61210% with 64 lines in your changes missing coverage. Please review.

Project coverage is 71.60%. Comparing base (6fb54a2) to head (61c9765).

Files with missing lines	Patch %	Lines
provers/groth16/bn_254/src/qap.rs	69.23%	40 Missing ⚠️
provers/groth16/bn_254/src/r1cs.rs	0.00%	23 Missing ⚠️
provers/groth16/bn_254/src/prover.rs	99.15%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #961      +/-   ##
==========================================
+ Coverage   71.32%   71.60%   +0.28%     
==========================================
  Files         155      163       +8     
  Lines       33537    34099     +562     
==========================================
+ Hits        23920    24418     +498     
- Misses       9617     9681      +64     

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