fundingManager: persist state in opening process.

Persists the state of a channel opening process after funding
transaction is confirmed. This tracks the messages sent to
the peer such that the process can be continued in case of a
restart. Also introduces that the receiver side forgets about
channel if funding transaction is not confirmed in 48hrs.

channeldb/channel.go

@@ -789,6 +789,12 @@ const (
 	// BreachClose indicates that one peer attempted to broadcast a prior
 	// _revoked_ channel state.
 	BreachClose
+
+	// FundingCanceled indicates that the channel never was fully opened before it
+	// was marked as closed in the database. This can happen if we or the remote
+	// fail at some point during the opening workflow, or we timeout waiting for
+	// the funding transaction to be confirmed.
+	FundingCanceled
 )
 
 // ChannelCloseSummary contains the final state of a channel at the point it