channeldb: convert to uniformly use new kvdb abstractions

In this commit, we migrate all the code in `channeldb` to only reference
the new `kvdb` package rather than `bbolt` directly.

In many instances, we need to add two version to fetch a bucket as both
read and write when needed. As an example, we add a new
`fetchChanBucketRw` function. This function is identical to
`fetchChanBucket`, but it will be used to fetch the main channel bucket
for all _write_ transactions. We need a new method as you can pass a
write transaction where a read is accepted, but not the other way around
due to the stronger typing of the new `kvdb` package.

channeldb/migration12/migration.go

@@ -3,7 +3,7 @@ package migration12
 import (
 	"bytes"
 
-	"github.com/coreos/bbolt"
+	"github.com/lightningnetwork/lnd/channeldb/kvdb"
 	"github.com/lightningnetwork/lnd/lnwire"
 )
 
@@ -12,11 +12,11 @@ var emptyFeatures = lnwire.NewFeatureVector(nil, nil)
 // MigrateInvoiceTLV migrates all existing invoice bodies over to be serialized
 // in a single TLV stream. In the process, we drop the Receipt field and add
 // PaymentAddr and Features to the invoice Terms.
-func MigrateInvoiceTLV(tx *bbolt.Tx) error {
+func MigrateInvoiceTLV(tx kvdb.RwTx) error {
 	log.Infof("Migrating invoice bodies to TLV, " +
 		"adding payment addresses and feature vectors.")
 
-	invoiceB := tx.Bucket(invoiceBucket)
+	invoiceB := tx.ReadWriteBucket(invoiceBucket)
 	if invoiceB == nil {
 		return nil
 	}

channeldb/migration12/migration_test.go

@@ -5,7 +5,7 @@ import (
 	"fmt"
 	"testing"
 
-	"github.com/coreos/bbolt"
+	"github.com/lightningnetwork/lnd/channeldb/kvdb"
 	"github.com/lightningnetwork/lnd/channeldb/migration12"
 	"github.com/lightningnetwork/lnd/channeldb/migtest"
 	"github.com/lightningnetwork/lnd/lntypes"
@@ -121,15 +121,15 @@ var (
 
 type migrationTest struct {
 	name            string
-	beforeMigration func(*bbolt.Tx) error
-	afterMigration  func(*bbolt.Tx) error
+	beforeMigration func(kvdb.RwTx) error
+	afterMigration  func(kvdb.RwTx) error
 }
 
 var migrationTests = []migrationTest{
 	{
 		name:            "no invoices",
-		beforeMigration: func(*bbolt.Tx) error { return nil },
-		afterMigration:  func(*bbolt.Tx) error { return nil },
+		beforeMigration: func(kvdb.RwTx) error { return nil },
+		afterMigration:  func(kvdb.RwTx) error { return nil },
 	},
 	{
 		name:            "zero htlcs",
@@ -145,9 +145,9 @@ var migrationTests = []migrationTest{
 
 // genBeforeMigration creates a closure that inserts an invoice serialized under
 // the old format under the test payment hash.
-func genBeforeMigration(beforeBytes []byte) func(*bbolt.Tx) error {
-	return func(tx *bbolt.Tx) error {
-		invoices, err := tx.CreateBucketIfNotExists(
+func genBeforeMigration(beforeBytes []byte) func(kvdb.RwTx) error {
+	return func(tx kvdb.RwTx) error {
+		invoices, err := tx.CreateTopLevelBucket(
 			invoiceBucket,
 		)
 		if err != nil {
@@ -162,9 +162,9 @@ func genBeforeMigration(beforeBytes []byte) func(*bbolt.Tx) error {
 // succeeded, but comparing the resulting encoding of the invoice to the
 // expected serialization. In addition, the decoded invoice is compared against
 // the expected invoice for equality.
-func genAfterMigration(afterBytes []byte) func(*bbolt.Tx) error {
-	return func(tx *bbolt.Tx) error {
-		invoices := tx.Bucket(invoiceBucket)
+func genAfterMigration(afterBytes []byte) func(kvdb.RwTx) error {
+	return func(tx kvdb.RwTx) error {
+		invoices := tx.ReadWriteBucket(invoiceBucket)
 		if invoices == nil {
 			return fmt.Errorf("invoice bucket not found")
 		}