EIP-7823 Modexp Upper Bounds

Documentation for tests/osaka/eip7823_modexp_upper_bounds@0c700940.

Generate fixtures for these test cases for Osaka with:

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

Tests EIP-7823: Set upper bounds for MODEXP

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