Switch to use containerd api types for transfer

[dmcgowan]

The transfer types are not in the main containerd repo, allowing callers to use the types without copying nerdbox's proto definition or importing nerdbox.

Any clients that use the transfer will need to be updated in tandem with this change.

[Copilot]

Pull request overview

This PR migrates the transfer stream protobuf types (ReadStream/WriteStream) from nerdbox-owned protos to the upstream github.com/containerd/containerd/api module, and removes nerdbox’s local datastream proto/generation artifacts accordingly.

Changes:

• Switch ReadStream/WriteStream typeurl marshaling/unmarshaling to use github.com/containerd/containerd/api/types/transfer.
• Remove the nerdbox datastream.proto and its generated datastream.pb.go.
• Update api/next.txtpb to drop the removed proto descriptor.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
internal/transfer/types.go	Uses containerd API transfer types for stream messages; keeps nerdbox type for ContainerFilesystem.
api/types/transfer/v1/datastream.pb.go	Removed generated Go for stream types now sourced from containerd API.
api/proto/nerdbox/types/transfer/v1/datastream.proto	Removed proto source for stream types now sourced from containerd API.
api/next.txtpb	Removed the datastream proto descriptor entry.

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[Copilot]

Pull request overview

Copilot reviewed 12 out of 12 changed files in this pull request and generated no new comments.

Comments suppressed due to low confidence (1)

internal/transfer/types.go:53

• The receiver variable name cf here is a holdover from the previous ContainerFilesystem type and is now misleading on ContainerPath. Renaming the receiver (e.g., cp) would improve readability and reduce confusion when scanning code that also deals with filesystem paths and streams.

func (cf *ContainerPath) MarshalAny(ctx context.Context, sm streaming.StreamCreator) (typeurl.Any, error) {
	return typeurl.MarshalAny(&transferpb.ContainerPath{
		ContainerID:       cf.ContainerID,
		Path:              cf.Path,
		NoWalk:            cf.NoWalk,
		PreserveOwnership: cf.PreserveOwnership,

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