On the Circuits uses the name `nTx` (and on the tests `maxTx`), but
Contracts `maxTx`. On Go we had both variables, but really only used
one, now at Go we use `MaxTx` to refer to the maximum number of
transactions.

- Implement Pipeline.prepareForgeBatchArgs()
- Add a minimal stress test for the coordinator (that also runs the
  synchronizer)
- Update txprocessor.ProcessTxs() to return valid results for batches without
  transactions
  	- Add the boilerplate for the corresponding test, leaving as TODO the
	  zkInput values
- Update prover client to use the same point format as proof server (projective)
- Update interface of TxSelector.GetCoordIdxs to also return the authorizations
  to create accounts that go with the l1CoordinatorTxs.