htlcswitch+peer: pass BestHeight to ChannelLinkConfig

This allows non-test usages of ChannelLinkConfig to omit the raw
htlcswitch.Switch pointer.

peer/brontide.go

@@ -813,7 +813,7 @@ func (p *Brontide) addLink(chanPoint *wire.OutPoint,
 		FetchLastChannelUpdate:  p.cfg.FetchLastChanUpdate,
 		HodlMask:                p.cfg.Hodl.Mask(),
 		Registry:                p.cfg.Invoices,
-		Switch:                  p.cfg.Switch,
+		BestHeight:              p.cfg.Switch.BestHeight,
 		Circuits:                p.cfg.Switch.CircuitModifier(),
 		ForwardPackets:          p.cfg.InterceptSwitch.ForwardPackets,
 		FwrdingPolicy:           *forwardingPolicy,