Add bn254 native contract bindings and tests

[Jim8y]

Description

Proposal neo-project/proposals#205 . Adds a bn254 native contract implementation that mirrors the Solidity/EVM precompile interface.
The contract now routes elliptic curve add, scalar multiplication, and pairing through Nethermind’s
MCL bindings, handling Ethereum’s big-endian payload layout and zero-on-error semantics. Unit
coverage includes the canonical Ethereum GeneralStateTests pairing vectors to ensure cross-chain
compatibility. The native manifest snapshot was refreshed so genesis exposes the new entry points.

Fixes # (issue)

Type of change

• Optimization (the change is only an optimization)
• Style (the change is only a code style for better maintenance or standard purpose)
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as
  expected)
• This change requires a documentation update

How Has This Been Tested?

• dotnet test tests/Neo.UnitTests/Neo.UnitTests.csproj --filter CryptoLib

Test Configuration:

• OS: same as CI image
• .NET SDK: 9.0.301
• Tests reused Ethereum fixtures (GeneralStateTests/stZeroKnowledge/ecpairing_inputs.json, commit
  c67e485ff8b5be9abc8ad15345ec21aa22e290d9)

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

[cschuchardt88]

BouncyCastle can do the curve

public static ECDomainParameters GetBN254G1DomainParameters()
{
    // Define the prime modulus 'p' of the base field.
    // p = 21888242871839275222246405745257275088696311157297823662689037894645226208583
    BigInteger p = new BigInteger("21888242871839275222246405745257275088696311157297823662689037894645226208583");

    // Define the curve equation y^2 = x^3 + a*x + b.
    // For BN254, a = 0 and b = 3.
    BigInteger a = BigInteger.Zero;
    BigInteger b = new BigInteger("3");

    // Define the order of the G1 group 'n'.
    // n = 21888242871839275222246405745257275088548364400416034343698204186575808495617
    BigInteger n = new BigInteger("21888242871839275222246405745257275088548364400416034343698204186575808495617");
    // The cofactor 'h' is usually a small integer. For BN254, it is (p+1-t)/n.
    BigInteger h = BigInteger.One;

    // Construct the finite field F_p.
    ECCurve curve = new FpCurve(p, a, b, n, h);

    // Define the G1 generator point coordinates (x, y).
    // x = 1, y = 2.
    BigInteger gx = new BigInteger("1");
    BigInteger gy = new BigInteger("2");

    // Create the ECPoint for the G1 generator.
    ECPoint g = curve.CreatePoint(gx, gy);

    // Combine parameters into an ECDomainParameters object.
    return new ECDomainParameters(curve, g, n, h);
}