Extend ethclient test, implement new TxID spec

- Implement new TxID spec that distinguishes L1UserTx and L1CoordinatorTx
- Replace some type []*Foo by []Foo
- Fix HistoryDB & L2DB bug: in case of error, a rollback was applied and the returned error was nil
- Reorder inserts in historydb.NewHistoryDB() to follow foreign key dependencies
- Add initial synchronizer test with test.Client (for now, only tested l1UserTxs, blocks, addToken)
- Update L1UserTx event in test.Client

common/pooll2tx.go

@@ -250,15 +250,15 @@ func (tx *PoolL2Tx) Tx() (*Tx, error) {
 	}, nil
 }
 
-// PoolL2TxsToL2Txs returns an array of []*L2Tx from an array of []*PoolL2Tx
-func PoolL2TxsToL2Txs(txs []*PoolL2Tx) ([]*L2Tx, error) {
-	var r []*L2Tx
+// PoolL2TxsToL2Txs returns an array of []L2Tx from an array of []PoolL2Tx
+func PoolL2TxsToL2Txs(txs []PoolL2Tx) ([]L2Tx, error) {
+	var r []L2Tx
 	for _, poolTx := range txs {
 		tx, err := poolTx.L2Tx()
 		if err != nil {
 			return nil, err
 		}
-		r = append(r, tx)
+		r = append(r, *tx)
 	}
 	return r, nil
 }