Replace go-ethereum's ABI API

[Xenomega]

go-ethereum's ABI API we rely on is meant to parse a full ABI and generate interfaces exactly matching those types, with native Go types. It is not meant to serialize individual ABI values in a human readable way (especially without a method definition) and there is no sensible intermediate representation for argument value representation. As such, the preparation for sequence mutation requires we resolve the abi.Method referenced when we first load a CallSequence from a corpus, so we have the correct provider to pack/unpack. In a future iteration, we should have ABI value types we can just pack directly without a method definition. It also requires type conversions through reflection.

Fixing this will clean up mutations/value generation a lot and strip away use of reflection to convert argument value types/structures.

However, for now we can proceed and can replace this later, so it's not worth detouring from our main objectives/timeline.