sqlcmig6: add transaction executor for Queries

This commit adds a helper struct that creates a `sqldb/v2` transaction
executor that wraps the `sqlcmig6.Queries` type.

db/sqlcmig6/db.go

@@ -3,6 +3,7 @@ package sqlcmig6
 import (
 	"context"
 	"database/sql"
+	"github.com/lightningnetwork/lnd/sqldb/v2"
 )
 
 type DBTX interface {
@@ -25,3 +26,19 @@ func (q *Queries) WithTx(tx *sql.Tx) *Queries {
 		db: tx,
 	}
 }
+
+type TxExecutor struct {
+	*sqldb.TransactionExecutor[*Queries]
+}
+
+func NewTxExecutor(baseDB *sqldb.BaseDB, queries *Queries) *TxExecutor {
+	executor := sqldb.NewTransactionExecutor(
+		baseDB, func(tx *sql.Tx) *Queries {
+			return queries.WithTx(tx)
+		},
+	)
+
+	return &TxExecutor{
+		TransactionExecutor: executor,
+	}
+}