Redo coordinator structure, connect API to node

- API:
	- Modify the constructor so that hardcoded rollup constants don't need
	  to be passed (introduce a `Config` and use `configAPI` internally)
- Common:
	- Update rollup constants with proper *big.Int when required
	- Add BidCoordinator and Slot structs used by the HistoryDB and
	  Synchronizer.
	- Add helper methods to AuctionConstants
	- AuctionVariables: Add column `DefaultSlotSetBidSlotNum` (in the SQL
	  table: `default_slot_set_bid_slot_num`), which indicates at which
	  slotNum does the `DefaultSlotSetBid` specified starts applying.
- Config:
	- Move coordinator exclusive configuration from the node config to the
	  coordinator config
- Coordinator:
	- Reorganize the code towards having the goroutines started and stopped
	  from the coordinator itself instead of the node.
	- Remove all stop and stopped channels, and use context.Context and
	  sync.WaitGroup instead.
	- Remove BatchInfo setters and assing variables directly
	- In ServerProof and ServerProofPool use context instead stop channel.
	- Use message passing to notify the coordinator about sync updates and
	  reorgs
	- Introduce the Pipeline, which can be started and stopped by the
	  Coordinator
	- Introduce the TxManager, which manages ethereum transactions (the
	  TxManager is also in charge of making the forge call to the rollup
	  smart contract).  The TxManager keeps ethereum transactions and:
	  	1. Waits for the transaction to be accepted
		2. Waits for the transaction to be confirmed for N blocks
	- In forge logic, first prepare a batch and then wait for an available
	  server proof to have all work ready once the proof server is ready.
	- Remove the `isForgeSequence` method which was querying the smart
	  contract, and instead use notifications sent by the Synchronizer to
	  figure out if it's forging time.
	- Update test (which is a minimal test to manually see if the
	  coordinator starts)
- HistoryDB:
	- Add method to get the number of batches in a slot (used to detect when
	  a slot has passed the bid winner forging deadline)
	- Add method to get the best bid and associated coordinator of a slot
	  (used to detect the forgerAddress that can forge the slot)
- General:
	- Rename some instances of `currentBlock` to `lastBlock` to be more
	  clear.
- Node:
	- Connect the API to the node and call the methods to update cached
	  state when the sync advances blocks.
	- Call methods to update Coordinator state when the sync advances blocks
	  and finds reorgs.
- Synchronizer:
	- Add Auction field in the Stats, which contain the current slot with
	  info about highest bidder and other related info required to know who
	  can forge in the current block.
	- Better organization of cached state:
		- On Sync, update the internal cached state
		- On Init or Reorg, load the state from HistoryDB into the
		  internal cached state.

db/historydb/historydb.go

@@ -290,6 +290,13 @@ func (hdb *HistoryDB) GetBatches(from, to common.BatchNum) ([]common.Batch, erro
 	return db.SlicePtrsToSlice(batches).([]common.Batch), err
 }
 
+// GetBatchesLen retrieve number of batches from the DB, given a slotNum
+func (hdb *HistoryDB) GetBatchesLen(slotNum int64) (int, error) {
+	row := hdb.db.QueryRow("SELECT COUNT(*) FROM batch WHERE slot_num = $1;", slotNum)
+	var batchesLen int
+	return batchesLen, row.Scan(&batchesLen)
+}
+
 // GetLastBatchNum returns the BatchNum of the latest forged batch
 func (hdb *HistoryDB) GetLastBatchNum() (common.BatchNum, error) {
 	row := hdb.db.QueryRow("SELECT batch_num FROM batch ORDER BY batch_num DESC LIMIT 1;")
@@ -318,16 +325,6 @@ func (hdb *HistoryDB) Reorg(lastValidBlock int64) error {
 	return err
 }
 
-// SyncPoD stores all the data that can be changed / added on a block in the PoD SC
-func (hdb *HistoryDB) SyncPoD(
-	blockNum uint64,
-	bids []common.Bid,
-	coordinators []common.Coordinator,
-	vars *common.AuctionVariables,
-) error {
-	return nil
-}
-
 // AddBids insert Bids into the DB
 func (hdb *HistoryDB) AddBids(bids []common.Bid) error { return hdb.addBids(hdb.db, bids) }
 func (hdb *HistoryDB) addBids(d meddler.DB, bids []common.Bid) error {
@@ -361,6 +358,27 @@ func (hdb *HistoryDB) GetBestBidAPI(slotNum *int64) (BidAPI, error) {
 	return *bid, err
 }
 
+// GetBestBidCoordinator returns the forger address of the highest bidder in a slot by slotNum
+func (hdb *HistoryDB) GetBestBidCoordinator(slotNum int64) (*common.BidCoordinator, error) {
+	bidCoord := &common.BidCoordinator{}
+	err := meddler.QueryRow(
+		hdb.db, bidCoord,
+		`SELECT (
+			SELECT default_slot_set_bid_slot_num
+			FROM auction_vars
+			WHERE default_slot_set_bid_slot_num <= $1
+			ORDER BY eth_block_num DESC LIMIT 1
+			),
+		bid.slot_num, bid.bid_value, bid.bidder_addr,
+		coordinator.forger_addr, coordinator.url
+		FROM bid
+		INNER JOIN coordinator ON bid.bidder_addr = coordinator.bidder_addr
+		WHERE bid.slot_num = $1 ORDER BY bid.item_id DESC LIMIT 1;`,
+		slotNum)
+
+	return bidCoord, err
+}
+
 // GetBestBidsAPI returns the best bid in specific slot by slotNum
 func (hdb *HistoryDB) GetBestBidsAPI(
 	minSlotNum, maxSlotNum *int64,
@@ -1244,6 +1262,7 @@ func (hdb *HistoryDB) SetInitialSCVars(rollup *common.RollupVariables,
 	rollup.EthBlockNum = 0
 	auction.EthBlockNum = 0
 	wDelayer.EthBlockNum = 0
+	auction.DefaultSlotSetBidSlotNum = 0
 	if err := hdb.setRollupVars(txn, rollup); err != nil {
 		return err
 	}