Remove gogo/protobuf and adjust types

This commit migrates containerd/protobuf from github.com/gogo/protobuf
to google.golang.org/protobuf and adjust types. Proto-generated structs
cannot be passed as values.

Fixes #6564.

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

protobuf/timestamp.go

@@ -19,30 +19,18 @@ package protobuf
 import (
 	"time"
 
-	"github.com/gogo/protobuf/types"
+	"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) *types.Timestamp {
-	pt, err := types.TimestampProto(from)
-	if err != nil {
-		panic(err)
-	}
-	return pt
+func ToTimestamp(from time.Time) *timestamppb.Timestamp {
+	return timestamppb.New(from)
 }
 
 // FromTimestamp creates time.Time from protobuf's Timestamp.
-func FromTimestamp(from *types.Timestamp) time.Time {
-	if from == nil {
-		// Return time.Time's zero value as like timestamppb.
-		return time.Time{}.UTC()
-	}
-	tt, err := types.TimestampFromProto(from)
-	if err != nil {
-		panic(err)
-	}
-	return tt
+func FromTimestamp(from *timestamppb.Timestamp) time.Time {
+	return from.AsTime()
 }