[BD-3584] fiojs next generation

Requirements

This starts the discussion on what the next gen fiojs should look like. Things to consider:

  • We want to move to a more “modular” architecture for fiojs where there is a “fio addin” on top of a core library.

  • Next generation eosio sdk will likely not be based on eosjs, but will instead likely be based on the Greymass eosio-core library.

  • So, first step for next gen fiojs would be to build a new library on top of eosio-core.