multi: use the "errors" package everywhere

Replace all usages of the "github.com/go-errors/errors" and
"github.com/pkg/errors" packages with the standard lib's "errors"
package. This ensures that error wrapping and `errors.Is` checks will
work as expected.

routing/bandwidth_test.go

@@ -1,10 +1,10 @@
 package routing
 
 import (
+	"errors"
 	"testing"
 
 	"github.com/btcsuite/btcd/btcutil"
-	"github.com/go-errors/errors"
 	"github.com/lightningnetwork/lnd/fn/v2"
 	"github.com/lightningnetwork/lnd/htlcswitch"
 	"github.com/lightningnetwork/lnd/lnwallet"