TxSel integrated with L2DB, Add L1CoordTx creation

- GetL2TxSelection & GetL1L2TxSelection integrated with dbs
- Create L1CoordinatorTx of type CreateAccountDeposit when a L2
requires it (and the AccountCreationAuth exists)

common/tx.go

@@ -1,49 +1,9 @@
 package common
 
 import (
-	"encoding/binary"
-	"fmt"
 	"math/big"
 )
 
-const (
-	idxBytesLen = 4
-	// maxIdxValue is the maximum value that Idx can have (32 bits: maxIdxValue=2**32-1)
-	maxIdxValue = 0xffffffff
-)
-
-// Idx represents the account Index in the MerkleTree
-type Idx uint32
-
-// Bytes returns a byte array representing the Idx
-func (idx Idx) Bytes() []byte {
-	var b [4]byte
-	binary.LittleEndian.PutUint32(b[:], uint32(idx))
-	return b[:]
-}
-
-// BigInt returns a *big.Int representing the Idx
-func (idx Idx) BigInt() *big.Int {
-	return big.NewInt(int64(idx))
-}
-
-// IdxFromBytes returns Idx from a byte array
-func IdxFromBytes(b []byte) (Idx, error) {
-	if len(b) != idxBytesLen {
-		return 0, fmt.Errorf("can not parse Idx, bytes len %d, expected 4", len(b))
-	}
-	idx := binary.LittleEndian.Uint32(b[:4])
-	return Idx(idx), nil
-}
-
-// IdxFromBigInt converts a *big.Int to Idx type
-func IdxFromBigInt(b *big.Int) (Idx, error) {
-	if b.Int64() > maxIdxValue {
-		return 0, ErrNumOverflow
-	}
-	return Idx(uint32(b.Int64())), nil
-}
-
 // TxID is the identifier of a Hermez network transaction
 type TxID Hash // Hash is a guess