Consolidate gogo/protobuf dependencies under our own protobuf package

This would make gogo/protobuf migration easier.

Signed-off-by: Kazuyoshi Kato <katokazu@amazon.com>

metrics/cgroups/common/type.go

@@ -22,7 +22,7 @@ package common
 import (
 	"context"
 
-	"github.com/gogo/protobuf/types"
+	"github.com/containerd/containerd/protobuf/types"
 )
 
 // Statable type that returns cgroup metrics