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.

contractcourt/log.go

@@ -5,14 +5,24 @@ import (
 	"github.com/lightningnetwork/lnd/build"
 )
 
-// log is a logger that is initialized with no output filters.  This
-// means the package will not perform any logging by default until the caller
-// requests it.
-var log btclog.Logger
+var (
+	// log is a logger that is initialized with no output filters.  This
+	// means the package will not perform any logging by default until the caller
+	// requests it.
+	log btclog.Logger
+
+	// brarLog is the logger used by the breach arb.
+	brarLog btclog.Logger
+
+	// utxnLog is the logger used by the utxo nursary.
+	utxnLog btclog.Logger
+)
 
 // The default amount of logging is none.
 func init() {
 	UseLogger(build.NewSubLogger("CNCT", nil))
+	UseBreachLogger(build.NewSubLogger("BRAR", nil))
+	UseNurseryLogger(build.NewSubLogger("UTXN", nil))
 }
 
 // DisableLog disables all library log output.  Logging output is disabled
@@ -28,6 +38,20 @@ func UseLogger(logger btclog.Logger) {
 	log = logger
 }
 
+// UseBreachLogger uses a specified Logger to output package logging info.
+// This should be used in preference to SetLogWriter if the caller is also
+// using btclog.
+func UseBreachLogger(logger btclog.Logger) {
+	brarLog = logger
+}
+
+// UseNurseryLogger uses a specified Logger to output package logging info.
+// This should be used in preference to SetLogWriter if the caller is also
+// using btclog.
+func UseNurseryLogger(logger btclog.Logger) {
+	utxnLog = logger
+}
+
 // logClosure is used to provide a closure over expensive logging operations so
 // don't have to be performed when the logging level doesn't warrant it.
 type logClosure func() string