Update coordinator, call all api update functions

- Common:
	- Rename Block.EthBlockNum to Block.Num to avoid unneeded repetition
- API:
	- Add UpdateNetworkInfoBlock to update just block information, to be
	  used when the node is not yet synchronized
- Node:
	- Call API.UpdateMetrics and UpdateRecommendedFee in a loop, with
	  configurable time intervals
- Synchronizer:
	- When mapping events by TxHash, use an array to support the possibility
	  of multiple calls of the same function happening in the same
	  transaction (for example, a smart contract in a single transaction
	  could call withdraw with delay twice, which would generate 2 withdraw
	  events, and 2 deposit events).
	- In Stats, keep entire LastBlock instead of just the blockNum
	- In Stats, add lastL1BatchBlock
	- Test Stats and SCVars
- Coordinator:
	- Enable writing the BatchInfo in every step of the pipeline to disk
	  (with JSON text files) for debugging purposes.
	- Move the Pipeline functionality from the Coordinator to its own struct
	  (Pipeline)
	- Implement shouldL1lL2Batch
	- In TxManager, implement logic to perform several attempts when doing
	  ethereum node RPC calls before considering the error. (Both for calls
	  to forgeBatch and transaction receipt)
	- In TxManager, reorganize the flow and note the specific points in
	  which actions are made when err != nil
- HistoryDB:
	- Implement GetLastL1BatchBlockNum: returns the blockNum of the latest
	  forged l1Batch, to help the coordinator decide when to forge an
	  L1Batch.
- EthereumClient and test.Client:
	- Update EthBlockByNumber to return the last block when the passed
	  number is -1.

coordinator/batch.go

@@ -1,6 +1,11 @@
 package coordinator
 
 import (
+	"encoding/json"
+	"fmt"
+	"io/ioutil"
+	"path"
+
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/hermeznetwork/hermez-node/common"
 	"github.com/hermeznetwork/hermez-node/eth"
@@ -33,4 +38,22 @@ type BatchInfo struct {
 	// FeesInfo
 	TxStatus TxStatus
 	EthTx    *types.Transaction
+	Receipt  *types.Receipt
+}
+
+// DebugStore is a debug function to store the BatchInfo as a json text file in
+// storePath
+func (b *BatchInfo) DebugStore(storePath string) error {
+	batchJSON, err := json.Marshal(b)
+	if err != nil {
+		return err
+	}
+	oldStateRoot := "null"
+	if b.ZKInputs != nil && b.ZKInputs.OldStateRoot != nil {
+		oldStateRoot = b.ZKInputs.OldStateRoot.String()
+	}
+	filename := fmt.Sprintf("%010d-%s.json", b.BatchNum, oldStateRoot)
+	// nolint reason: 0640 allows rw to owner and r to group
+	//nolint:gosec
+	return ioutil.WriteFile(path.Join(storePath, filename), batchJSON, 0640)
 }