Remove github.com/gogo/protobuf again

While we need to support CRI v1alpha2, the implementation doesn't have
to be tied to gogo/protobuf.

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

pkg/cri/util/alpha.go

@@ -0,0 +1,52 @@
+/*
+   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 util
+
+import (
+	"github.com/containerd/containerd/protobuf/proto"
+	"google.golang.org/protobuf/reflect/protoreflect"
+)
+
+func AlphaReqToV1Req(
+	alphar protoreflect.ProtoMessage,
+	v1r interface{ Unmarshal(_ []byte) error },
+) error {
+	p, err := proto.Marshal(alphar)
+	if err != nil {
+		return err
+	}
+
+	if err = v1r.Unmarshal(p); err != nil {
+		return err
+	}
+	return nil
+}
+
+func V1RespToAlphaResp(
+	v1res interface{ Marshal() ([]byte, error) },
+	alphares protoreflect.ProtoMessage,
+) error {
+	p, err := v1res.Marshal()
+	if err != nil {
+		return err
+	}
+
+	if err = proto.Unmarshal(p, alphares); err != nil {
+		return err
+	}
+	return nil
+}