contractcourt: persist remote outgoing htlc claim outcome on disk

When a remote peer claims one of our outgoing htlcs on chain, we do
not care whether they claimed with multiple stages. We simply store
the claim outgome then forget the resolver.

channeldb/reports.go

@@ -52,6 +52,9 @@ const (
 
 	// ResolverTypeIncomingHtlc represents resolution of an incoming htlc.
 	ResolverTypeIncomingHtlc ResolverType = 1
+
+	// ResolverTypeOutgoingHtlc represents resolution of an outgoing htlc.
+	ResolverTypeOutgoingHtlc ResolverType = 2
 )
 
 // ResolverOutcome indicates the outcome for the resolver that that the contract