update param for initWithSigners to use Signer[] to dedupe code in test cases
update param for initWithSigners to use Signer[] to dedupe code in test cases

ethereum/ethereumjs-vm,ethereumjs/ethereumjs-vm,ethereumjs/ethereumjs-vm,ethereumjs/ethereumjs-vm,ethereumjs/ethereumjs-vm,ethereumjs/ethereumjs-vm