lnd+contractcourt: add more debug logs

This commit adds more debug logs for witness beacon and channel
arbitrator.

contractcourt/htlc_incoming_contest_resolver.go

@@ -140,6 +140,9 @@ func (h *htlcIncomingContestResolver) Resolve() (ContractResolver, error) {
 		return nil, errResolverShuttingDown
 	}
 
+	log.Debugf("%T(%v): Resolving incoming HTLC(expiry=%v, height=%v)", h,
+		h.htlcResolution.ClaimOutpoint, h.htlcExpiry, currentHeight)
+
 	// We'll first check if this HTLC has been timed out, if so, we can
 	// return now and mark ourselves as resolved. If we're past the point of
 	// expiry of the HTLC, then at this point the sender can sweep it, so