✨(gentest): use evm_bytes to generate python opcode in tests

[danceratopz]

Currently, evm code is written as a hex string in the generated test. This could be made more readable by converting the bytecode to the Opcodes mini-lang using evm_bytes (as used here):

execution-spec-tests/tests/shanghai/eip3855_push0/test_push0.py

Line 61 in 802467c

Op.PUSH1(4) + Op.JUMP + Op.PUSH0 + Op.JUMPDEST + Op.SSTORE(Op.PUSH0, 1) + Op.STOP,

The first todo would be probably to check whether gentest correctly generates tests that have a smart contract interaction 🙂

Note: evm_bytes_to_python was renamed to evm_bytes in #844