refactor(setup): remove initPhase2 and add extract vKey method

[ctrlc03]

fix #50

• [x] Remove these lines and use existing PTAU instead of thats being created ptau2init there
• [x] Update base URL for Perpetual Powers of Tau urls
• [x] Add an extract function that looks for the zKey (w.r.t circuit name and configured protocol) and generates the vKey
• [x] Add CLI wrapper that calls extract
• [x] No need to check if PTAUs for larger constrain counts exist as you mentioned above, but maybe we can add a comment TODO: check for performance gains when larger PTAUs are found instead of the target PTAU; I want to check that out sometime :)

[ctrlc03]

all good! added just a single line change to not remove the downloaded ptau

thanks for the review 🙂

[erhant]

thanks for the quick PR 🥂