Add data to get_witnesses end point

Per checking witness data returned via hafbe endpoint for witnesses (https://gitlab.syncad.com/hive/haf_block_explorer/-/blob/develop/endpoints/witnesses/get_witnesses.sql?ref_type=heads) data seems limited compared to data returned by condenser_api.get_witnesses_by_vote

We want to expand the endpoint to include the values of last_confirmed_block_num and account_creation_fee (found under props) normally returned by condenser.get_witnesses_by_vote

Thanks!