[#1324] services/tree: Implement Object Tree Service

Object Tree Service allows changing trees assotiated with
the container in runtime.

Signed-off-by: Evgenii Stratonikov <evgeniy@nspcc.ru>

cmd/neofs-node/tree.go

@@ -0,0 +1,41 @@
+package main
+
+import (
+	"context"
+	"net"
+
+	treeconfig "github.com/nspcc-dev/neofs-node/cmd/neofs-node/config/tree"
+	"github.com/nspcc-dev/neofs-node/pkg/services/tree"
+	"google.golang.org/grpc"
+)
+
+func initTreeService(c *cfg) {
+	endpoint := treeconfig.GRPC(c.appCfg).Endpoint()
+	if endpoint == treeconfig.GRPCEndpointDefault {
+		return
+	}
+
+	treeSvc := tree.New(
+		tree.WithContainerSource(c.cfgObject.cnrSource),
+		tree.WithNetmapSource(c.netMapSource),
+		tree.WithPrivateKey(&c.key.PrivateKey),
+		tree.WithLogger(c.log),
+		tree.WithStorage(c.cfgObject.cfgLocalStorage.localStorage))
+
+	treeServer := grpc.NewServer()
+
+	c.onShutdown(func() {
+		stopGRPC("NeoFS Tree Service API", treeServer, c.log)
+		treeSvc.Shutdown()
+	})
+
+	lis, err := net.Listen("tcp", endpoint)
+	fatalOnErr(err)
+
+	tree.RegisterTreeServiceServer(treeServer, treeSvc)
+
+	c.workers = append(c.workers, newWorkerFromFunc(func(ctx context.Context) {
+		treeSvc.Start(ctx)
+		fatalOnErr(treeServer.Serve(lis))
+	}))
+}