multi: move breach arbiter and utxo nursery into contractcourt package

In this commit, we take an initial step towards converting the existing
breach arbiter and utxo nursery logic into contract resolvers by moving
the files as is, into the `contractcourt` pacakge.

This commit is primarily move only, though we had to massage some
interfaces and config names along the way to make things compile and the
tests run properly.

htlcswitch/switch.go

@@ -80,26 +80,12 @@ type plexPacket struct {
 	err chan error
 }
 
-// ChannelCloseType is an enum which signals the type of channel closure the
-// peer should execute.
-type ChannelCloseType uint8
-
-const (
-	// CloseRegular indicates a regular cooperative channel closure
-	// should be attempted.
-	CloseRegular ChannelCloseType = iota
-
-	// CloseBreach indicates that a channel breach has been detected, and
-	// the link should immediately be marked as unavailable.
-	CloseBreach
-)
-
 // ChanClose represents a request which close a particular channel specified by
 // its id.
 type ChanClose struct {
 	// CloseType is a variable which signals the type of channel closure the
 	// peer should execute.
-	CloseType ChannelCloseType
+	CloseType contractcourt.ChannelCloseType
 
 	// ChanPoint represent the id of the channel which should be closed.
 	ChanPoint *wire.OutPoint
@@ -1454,7 +1440,8 @@ func (s *Switch) teardownCircuit(pkt *htlcPacket) error {
 // a starting point for close negotiation. The deliveryScript parameter is an
 // optional parameter which sets a user specified script to close out to.
 func (s *Switch) CloseLink(chanPoint *wire.OutPoint,
-	closeType ChannelCloseType, targetFeePerKw chainfee.SatPerKWeight,
+	closeType contractcourt.ChannelCloseType,
+	targetFeePerKw chainfee.SatPerKWeight,
 	deliveryScript lnwire.DeliveryAddress) (chan interface{}, chan error) {
 
 	// TODO(roasbeef) abstract out the close updates.