ecrecover implementation in EVMMAX

[Paweł Bylica]

• Input validation
• Point "decompression"
  • Implement field sqrt
  • Using sqrt find the y coordinate of of R taking r and v from the signature. Curve is y² = x³+7.
• "Double" point multiplication
  • Implement point multiplication: affine → projected
  • Implement point addition: projected → projected
  • Implement conversion: projected → affine
• ECDSA public key recovery
  • Convert message hash e to z field element
  • Recover public key (a point)
• Convert public key to address

[Paweł Bylica]

Done in #688.