EIP-7823 Modexp Upper Bounds

Documentation for tests/osaka/eip7823_modexp_upper_bounds@7b8124a7.

Generate fixtures for these test cases for Bpo2 with:

fill -v tests/osaka/eip7823_modexp_upper_bounds --fork Bpo2

Tests EIP-7823: Set upper bounds for MODEXP.

Test cases for EIP-7823: Set upper bounds for MODEXP.