Add TxID calculation & New{Layer}Tx Type

Add TxID calculation & New{Layer}Tx Type

New{Layer}Tx methods that compute the `TxID` & `TxType` values from the
transaction values:
- NewL1Tx
- NewL2Tx
- NewPoolL2Tx

Add TxID Scanner & Valuer for database/sql

HistoryDB & L2DB & API packages tests will need to be addapted to the
TestTransaction generation once is done.

db/statedb/statedb.go

@@ -185,7 +185,7 @@ func (s *StateDB) Reset(batchNum common.BatchNum) error {
 			return err
 		}
 		s.db = sto
-		s.idx = 0
+		s.idx = 255
 		s.currentBatch = batchNum
 		return nil
 	}