Previous to this commit, there were cases where being
len(nonForgableL2Txs)>maxL2Txs and nonForgableL2Txs have bigger fee than
forgableL2Txs, the forgableTxs where never forged, neither the
nonForgableTxs. Now, the TxSelector first forges the forgableTxs (which
are forgable for the initial state of the accounts (balances & nonces),
and then the nonForgableL2Txs, which may be unblocked once the forgable
ones have been processed.