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.