refactor: remove vendored Go repos, keep only .proto files

wfe-containerd-protos/proto/api/services/streaming/v1/streaming.proto

@@ -0,0 +1,31 @@
+/*
+   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.
+*/
+
+syntax = "proto3";
+
+package containerd.services.streaming.v1;
+
+import "google/protobuf/any.proto";
+
+option go_package = "github.com/containerd/containerd/api/services/streaming/v1;streaming";
+
+service Streaming {
+  rpc Stream(stream google.protobuf.Any) returns (stream google.protobuf.Any);
+}
+
+message StreamInit {
+  string id = 1;
+}