multi: introduce new paymentsDB package

We introduce a new package paymentsDB and start by moving the
payment specifc errors from the channeldb package to the
paymentsDB package. We also fix linter issues which showed up
due to changing this code part.

routing/control_tower_test.go

@@ -13,6 +13,7 @@ import (
 	"github.com/davecgh/go-spew/spew"
 	"github.com/lightningnetwork/lnd/channeldb"
 	"github.com/lightningnetwork/lnd/lntypes"
+	paymentsdb "github.com/lightningnetwork/lnd/payments/db"
 	"github.com/lightningnetwork/lnd/routing/route"
 	"github.com/stretchr/testify/require"
 )
@@ -53,7 +54,7 @@ func TestControlTowerSubscribeUnknown(t *testing.T) {
 
 	// Subscription should fail when the payment is not known.
 	_, err := pControl.SubscribePayment(lntypes.Hash{1})
-	require.ErrorIs(t, err, channeldb.ErrPaymentNotInitiated)
+	require.ErrorIs(t, err, paymentsdb.ErrPaymentNotInitiated)
 }
 
 // TestControlTowerSubscribeSuccess tests that payment updates for a