contractcourt: save htlc success resolvers, including first stage

Checkpoint our htlc claims with on chain reasolutions, including our
first stage success tx where required.

channeldb/reports.go

@@ -77,6 +77,11 @@ const (
 	// ResolverOutcomeTimeout indicates that a contract was timed out on
 	// chain.
 	ResolverOutcomeTimeout ResolverOutcome = 3
+
+	// ResolverOutcomeFirstStage indicates that a htlc had to be claimed
+	// over two stages, with this outcome representing the confirmation
+	// of our success/timeout tx.
+	ResolverOutcomeFirstStage ResolverOutcome = 4
 )
 
 // ResolverReport provides an account of the outcome of a resolver. This differs