contractcourt: fix linter funlen

Refactor the `Start` method to fix the linter error:
```
contractcourt/chain_arbitrator.go:568: Function 'Start' is too long (242 > 200) (funlen)
```

contractcourt/chain_arbitrator.go

@@ -583,137 +583,17 @@ func (c *ChainArbitrator) Start(beat chainio.Blockbeat) error {
 
 	// First, we'll fetch all the channels that are still open, in order to
 	// collect them within our set of active contracts.
-	openChannels, err := c.chanSource.ChannelStateDB().FetchAllChannels()
-	if err != nil {
+	if err := c.loadOpenChannels(); err != nil {
 		return err
 	}
 
-	if len(openChannels) > 0 {
-		log.Infof("Creating ChannelArbitrators for %v active channels",
-			len(openChannels))
-	}
-
-	// For each open channel, we'll configure then launch a corresponding
-	// ChannelArbitrator.
-	for _, channel := range openChannels {
-		chanPoint := channel.FundingOutpoint
-		channel := channel
-
-		// First, we'll create an active chainWatcher for this channel
-		// to ensure that we detect any relevant on chain events.
-		breachClosure := func(ret *lnwallet.BreachRetribution) error {
-			return c.cfg.ContractBreach(chanPoint, ret)
-		}
-
-		chainWatcher, err := newChainWatcher(
-			chainWatcherConfig{
-				chanState:           channel,
-				notifier:            c.cfg.Notifier,
-				signer:              c.cfg.Signer,
-				isOurAddr:           c.cfg.IsOurAddress,
-				contractBreach:      breachClosure,
-				extractStateNumHint: lnwallet.GetStateNumHint,
-				auxLeafStore:        c.cfg.AuxLeafStore,
-				auxResolver:         c.cfg.AuxResolver,
-			},
-		)
-		if err != nil {
-			return err
-		}
-
-		c.activeWatchers[chanPoint] = chainWatcher
-		channelArb, err := newActiveChannelArbitrator(
-			channel, c, chainWatcher.SubscribeChannelEvents(),
-		)
-		if err != nil {
-			return err
-		}
-
-		c.activeChannels[chanPoint] = channelArb
-
-		// Republish any closing transactions for this channel.
-		err = c.republishClosingTxs(channel)
-		if err != nil {
-			log.Errorf("Failed to republish closing txs for "+
-				"channel %v", chanPoint)
-		}
-	}
-
 	// In addition to the channels that we know to be open, we'll also
 	// launch arbitrators to finishing resolving any channels that are in
 	// the pending close state.
-	closingChannels, err := c.chanSource.ChannelStateDB().FetchClosedChannels(
-		true,
-	)
-	if err != nil {
+	if err := c.loadPendingCloseChannels(); err != nil {
 		return err
 	}
 
-	if len(closingChannels) > 0 {
-		log.Infof("Creating ChannelArbitrators for %v closing channels",
-			len(closingChannels))
-	}
-
-	// Next, for each channel is the closing state, we'll launch a
-	// corresponding more restricted resolver, as we don't have to watch
-	// the chain any longer, only resolve the contracts on the confirmed
-	// commitment.
-	//nolint:ll
-	for _, closeChanInfo := range closingChannels {
-		// We can leave off the CloseContract and ForceCloseChan
-		// methods as the channel is already closed at this point.
-		chanPoint := closeChanInfo.ChanPoint
-		arbCfg := ChannelArbitratorConfig{
-			ChanPoint:             chanPoint,
-			ShortChanID:           closeChanInfo.ShortChanID,
-			ChainArbitratorConfig: c.cfg,
-			ChainEvents:           &ChainEventSubscription{},
-			IsPendingClose:        true,
-			ClosingHeight:         closeChanInfo.CloseHeight,
-			CloseType:             closeChanInfo.CloseType,
-			PutResolverReport: func(tx kvdb.RwTx,
-				report *channeldb.ResolverReport) error {
-
-				return c.chanSource.PutResolverReport(
-					tx, c.cfg.ChainHash, &chanPoint, report,
-				)
-			},
-			FetchHistoricalChannel: func() (*channeldb.OpenChannel, error) {
-				chanStateDB := c.chanSource.ChannelStateDB()
-				return chanStateDB.FetchHistoricalChannel(&chanPoint)
-			},
-			FindOutgoingHTLCDeadline: func(
-				htlc channeldb.HTLC) fn.Option[int32] {
-
-				return c.FindOutgoingHTLCDeadline(
-					closeChanInfo.ShortChanID, htlc,
-				)
-			},
-		}
-		chanLog, err := newBoltArbitratorLog(
-			c.chanSource.Backend, arbCfg, c.cfg.ChainHash, chanPoint,
-		)
-		if err != nil {
-			return err
-		}
-		arbCfg.MarkChannelResolved = func() error {
-			if c.cfg.NotifyFullyResolvedChannel != nil {
-				c.cfg.NotifyFullyResolvedChannel(chanPoint)
-			}
-
-			return c.ResolveContract(chanPoint)
-		}
-
-		// We create an empty map of HTLC's here since it's possible
-		// that the channel is in StateDefault and updateActiveHTLCs is
-		// called. We want to avoid writing to an empty map. Since the
-		// channel is already in the process of being resolved, no new
-		// HTLCs will be added.
-		c.activeChannels[chanPoint] = NewChannelArbitrator(
-			arbCfg, make(map[HtlcSetKey]htlcSet), chanLog,
-		)
-	}
-
 	// Now, we'll start all chain watchers in parallel to shorten start up
 	// duration. In neutrino mode, this allows spend registrations to take
 	// advantage of batch spend reporting, instead of doing a single rescan
@@ -765,7 +645,7 @@ func (c *ChainArbitrator) Start(beat chainio.Blockbeat) error {
 	// transaction.
 	var startStates map[wire.OutPoint]*chanArbStartState
 
-	err = kvdb.View(c.chanSource, func(tx walletdb.ReadTx) error {
+	err := kvdb.View(c.chanSource, func(tx walletdb.ReadTx) error {
 		for _, arbitrator := range c.activeChannels {
 			startState, err := arbitrator.getStartState(tx)
 			if err != nil {
@@ -1332,3 +1212,147 @@ func (c *ChainArbitrator) FindOutgoingHTLCDeadline(scid lnwire.ShortChannelID,
 func (c *ChainArbitrator) Name() string {
 	return "ChainArbitrator"
 }
+
+// loadOpenChannels loads all channels that are currently open in the database
+// and registers them with the chainWatcher for future notification.
+func (c *ChainArbitrator) loadOpenChannels() error {
+	openChannels, err := c.chanSource.ChannelStateDB().FetchAllChannels()
+	if err != nil {
+		return err
+	}
+
+	if len(openChannels) == 0 {
+		return nil
+	}
+
+	log.Infof("Creating ChannelArbitrators for %v active channels",
+		len(openChannels))
+
+	// For each open channel, we'll configure then launch a corresponding
+	// ChannelArbitrator.
+	for _, channel := range openChannels {
+		chanPoint := channel.FundingOutpoint
+		channel := channel
+
+		// First, we'll create an active chainWatcher for this channel
+		// to ensure that we detect any relevant on chain events.
+		breachClosure := func(ret *lnwallet.BreachRetribution) error {
+			return c.cfg.ContractBreach(chanPoint, ret)
+		}
+
+		chainWatcher, err := newChainWatcher(
+			chainWatcherConfig{
+				chanState:           channel,
+				notifier:            c.cfg.Notifier,
+				signer:              c.cfg.Signer,
+				isOurAddr:           c.cfg.IsOurAddress,
+				contractBreach:      breachClosure,
+				extractStateNumHint: lnwallet.GetStateNumHint,
+				auxLeafStore:        c.cfg.AuxLeafStore,
+				auxResolver:         c.cfg.AuxResolver,
+			},
+		)
+		if err != nil {
+			return err
+		}
+
+		c.activeWatchers[chanPoint] = chainWatcher
+		channelArb, err := newActiveChannelArbitrator(
+			channel, c, chainWatcher.SubscribeChannelEvents(),
+		)
+		if err != nil {
+			return err
+		}
+
+		c.activeChannels[chanPoint] = channelArb
+
+		// Republish any closing transactions for this channel.
+		err = c.republishClosingTxs(channel)
+		if err != nil {
+			log.Errorf("Failed to republish closing txs for "+
+				"channel %v", chanPoint)
+		}
+	}
+
+	return nil
+}
+
+// loadPendingCloseChannels loads all channels that are currently pending
+// closure in the database and registers them with the ChannelArbitrator to
+// continue the resolution process.
+func (c *ChainArbitrator) loadPendingCloseChannels() error {
+	chanStateDB := c.chanSource.ChannelStateDB()
+
+	closingChannels, err := chanStateDB.FetchClosedChannels(true)
+	if err != nil {
+		return err
+	}
+
+	if len(closingChannels) == 0 {
+		return nil
+	}
+
+	log.Infof("Creating ChannelArbitrators for %v closing channels",
+		len(closingChannels))
+
+	// Next, for each channel is the closing state, we'll launch a
+	// corresponding more restricted resolver, as we don't have to watch
+	// the chain any longer, only resolve the contracts on the confirmed
+	// commitment.
+	//nolint:ll
+	for _, closeChanInfo := range closingChannels {
+		// We can leave off the CloseContract and ForceCloseChan
+		// methods as the channel is already closed at this point.
+		chanPoint := closeChanInfo.ChanPoint
+		arbCfg := ChannelArbitratorConfig{
+			ChanPoint:             chanPoint,
+			ShortChanID:           closeChanInfo.ShortChanID,
+			ChainArbitratorConfig: c.cfg,
+			ChainEvents:           &ChainEventSubscription{},
+			IsPendingClose:        true,
+			ClosingHeight:         closeChanInfo.CloseHeight,
+			CloseType:             closeChanInfo.CloseType,
+			PutResolverReport: func(tx kvdb.RwTx,
+				report *channeldb.ResolverReport) error {
+
+				return c.chanSource.PutResolverReport(
+					tx, c.cfg.ChainHash, &chanPoint, report,
+				)
+			},
+			FetchHistoricalChannel: func() (*channeldb.OpenChannel, error) {
+				return chanStateDB.FetchHistoricalChannel(&chanPoint)
+			},
+			FindOutgoingHTLCDeadline: func(
+				htlc channeldb.HTLC) fn.Option[int32] {
+
+				return c.FindOutgoingHTLCDeadline(
+					closeChanInfo.ShortChanID, htlc,
+				)
+			},
+		}
+		chanLog, err := newBoltArbitratorLog(
+			c.chanSource.Backend, arbCfg, c.cfg.ChainHash, chanPoint,
+		)
+		if err != nil {
+			return err
+		}
+		arbCfg.MarkChannelResolved = func() error {
+			if c.cfg.NotifyFullyResolvedChannel != nil {
+				c.cfg.NotifyFullyResolvedChannel(chanPoint)
+			}
+
+			return c.ResolveContract(chanPoint)
+		}
+
+		// We create an empty map of HTLC's here since it's possible
+		// that the channel is in StateDefault and updateActiveHTLCs is
+		// called. We want to avoid writing to an empty map. Since the
+		// channel is already in the process of being resolved, no new
+		// HTLCs will be added.
+		c.activeChannels[chanPoint] = NewChannelArbitrator(
+			arbCfg, make(map[HtlcSetKey]htlcSet), chanLog,
+		)
+	}
+
+	return nil
+}

contractcourt/commit_sweep_resolver.go

@@ -165,6 +165,10 @@ func (c *commitSweepResolver) getCommitTxConfHeight() (uint32, error) {
 // returned.
 //
 // NOTE: This function MUST be run as a goroutine.
+
+// TODO(yy): fix the funlen in the next PR.
+//
+//nolint:funlen
 func (c *commitSweepResolver) Resolve() (ContractResolver, error) {
 	// If we're already resolved, then we can exit early.
 	if c.resolved {