refactor: move graph related DB code to graph/db from channeldb

This is a pure refactor commit. It moves over all the graph related CRUD
code from `channeldb` to `graph/db`.

lnrpc/devrpc/dev_server.go

@@ -16,8 +16,8 @@ import (
 	"github.com/btcsuite/btcd/chaincfg/chainhash"
 	"github.com/btcsuite/btcd/wire"
 	"github.com/grpc-ecosystem/grpc-gateway/v2/runtime"
-	"github.com/lightningnetwork/lnd/channeldb"
 	"github.com/lightningnetwork/lnd/fn"
+	graphdb "github.com/lightningnetwork/lnd/graph/db"
 	"github.com/lightningnetwork/lnd/graph/db/models"
 	"github.com/lightningnetwork/lnd/lncfg"
 	"github.com/lightningnetwork/lnd/lnrpc"
@@ -227,7 +227,7 @@ func (s *Server) ImportGraph(ctx context.Context,
 
 	var err error
 	for _, rpcNode := range graph.Nodes {
-		node := &channeldb.LightningNode{
+		node := &graphdb.LightningNode{
 			HaveNodeAnnouncement: true,
 			LastUpdate: time.Unix(
 				int64(rpcNode.LastUpdate), 0,