feat: implement abi2sol

[DaniPopes]

Motivation

Rewrite code that generates Solidity tokens from a JsonAbi in sol-macro to use strings in json-abi.

Solution

PR Checklist

• Added Tests
• Added Documentation
• [no] Breaking changes

[prestwich]

it seems like we want to unify this to_sol with syn-solidity somehow, no? rather than assembling strings like this, we should consider converting abi json to syn-solidity types and then having a pipeline for converting syn-solidity into sol files?

[DaniPopes]

I want this to produce a string which can be used in both. There is no need to implement it specifically for the ast

[prestwich]

my point is that "converting type specifications to solidity strings" is probably a common action that we should capture in a single location. should we capture it here, or elsewhere?

[DaniPopes]

@prestwich thinking too far ahead :) This is fine for now.