Move protobuf package under pkg

Signed-off-by: Derek McGowan <derek@mcg.dev>

pkg/protobuf/timestamp.go

@@ -0,0 +1,36 @@
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package protobuf
+
+import (
+	"time"
+
+	"google.golang.org/protobuf/types/known/timestamppb"
+)
+
+// Once we migrate off from gogo/protobuf, we can use the function below, which don't return any errors.
+// https://github.com/protocolbuffers/protobuf-go/blob/v1.28.0/types/known/timestamppb/timestamp.pb.go#L200-L208
+
+// ToTimestamp creates protobuf's Timestamp from time.Time.
+func ToTimestamp(from time.Time) *timestamppb.Timestamp {
+	return timestamppb.New(from)
+}
+
+// FromTimestamp creates time.Time from protobuf's Timestamp.
+func FromTimestamp(from *timestamppb.Timestamp) time.Time {
+	return from.AsTime()
+}