✨(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): https://github.com/ethereum/execution-spec-tests/blob/802467c890e55cac89ad903585f01e440f701728/tests/shanghai/eip3855_push0/test_push0.py#L61

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

Note: evm_bytes_to_python was renamed to evm_bytes in #844