api/services/instrospection: add PluginInfo

The new `PlunginInfo()` call can be used for instrospecting the details
of the runtime plugin.

```console
$ ctr plugins inspect-runtime --runtime=io.containerd.runc.v2 --runc-binary=runc
{
    "Name": "io.containerd.runc.v2",
    "Version": {
        "Version": "v2.0.0-beta.0-XX-gXXXXXXXXX.m",
        "Revision": "v2.0.0-beta.0-XX-gXXXXXXXXX.m"
    },
    "Options": {
        "binary_name": "runc"
    },
    "Features": {
        "ociVersionMin": "1.0.0",
        "ociVersionMax": "1.1.0-rc.2",
        ...,
    },
    "Annotations": null
}
```

The shim binary has to support `-info` flag, see `runtime/v2/README.md`

Replaces PR 8509 (`api/services/task: add RuntimeInfo()`)

Co-authored-by: Derek McGowan <derek@mcg.dev>
Signed-off-by: Akihiro Suda <akihiro.suda.cz@hco.ntt.co.jp>

client/client.go

@@ -58,11 +58,13 @@ import (
 	"github.com/containerd/containerd/v2/pkg/namespaces"
 	"github.com/containerd/containerd/v2/plugins"
 	"github.com/containerd/containerd/v2/plugins/services/introspection"
+	"github.com/containerd/containerd/v2/protobuf"
 	ptypes "github.com/containerd/containerd/v2/protobuf/types"
 	"github.com/containerd/platforms"
 	"github.com/containerd/typeurl/v2"
 	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
 	"github.com/opencontainers/runtime-spec/specs-go"
+	"github.com/opencontainers/runtime-spec/specs-go/features"
 	"golang.org/x/sync/semaphore"
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/backoff"
@@ -78,6 +80,7 @@ func init() {
 	typeurl.Register(&specs.Process{}, prefix, "opencontainers/runtime-spec", major, "Process")
 	typeurl.Register(&specs.LinuxResources{}, prefix, "opencontainers/runtime-spec", major, "LinuxResources")
 	typeurl.Register(&specs.WindowsResources{}, prefix, "opencontainers/runtime-spec", major, "WindowsResources")
+	typeurl.Register(&features.Features{}, prefix, "opencontainers/runtime-spec", major, "features", "Features")
 }
 
 // New returns a new containerd client that is connected to the containerd
@@ -871,3 +874,76 @@ func (c *Client) GetSnapshotterCapabilities(ctx context.Context, snapshotterName
 	sn := resp.Plugins[0]
 	return sn.Capabilities, nil
 }
+
+type RuntimeVersion struct {
+	Version  string
+	Revision string
+}
+
+type RuntimeInfo struct {
+	Name        string
+	Version     RuntimeVersion
+	Options     interface{}
+	Features    interface{}
+	Annotations map[string]string
+}
+
+func (c *Client) RuntimeInfo(ctx context.Context, runtimePath string, runtimeOptions interface{}) (*RuntimeInfo, error) {
+	rt := c.runtime
+	if runtimePath != "" {
+		rt = runtimePath
+	}
+	rr := &apitypes.RuntimeRequest{
+		RuntimePath: rt,
+	}
+	var err error
+	if runtimeOptions != nil {
+		rr.Options, err = protobuf.MarshalAnyToProto(runtimeOptions)
+		if err != nil {
+			return nil, fmt.Errorf("failed to marshal %T: %w", runtimeOptions, err)
+		}
+	}
+	options, err := protobuf.MarshalAnyToProto(rr)
+	if err != nil {
+		return nil, fmt.Errorf("failed to marshal runtime requst: %w", err)
+	}
+
+	s := c.IntrospectionService()
+
+	req := &introspectionapi.PluginInfoRequest{
+		Type:    string(plugins.RuntimePluginV2),
+		ID:      "task",
+		Options: options,
+	}
+
+	resp, err := s.PluginInfo(ctx, req)
+	if err != nil {
+		return nil, err
+	}
+
+	var info apitypes.RuntimeInfo
+	if err := typeurl.UnmarshalTo(resp.Extra, &info); err != nil {
+		return nil, fmt.Errorf("failed to get runtime info from plugin info: %w", err)
+	}
+
+	var result RuntimeInfo
+	result.Name = info.Name
+	if info.Version != nil {
+		result.Version.Version = info.Version.Version
+		result.Version.Revision = info.Version.Revision
+	}
+	if info.Options != nil {
+		result.Options, err = typeurl.UnmarshalAny(info.Options)
+		if err != nil {
+			return nil, fmt.Errorf("failed to unmarshal RuntimeInfo.Options (%T): %w", info.Options, err)
+		}
+	}
+	if info.Features != nil {
+		result.Features, err = typeurl.UnmarshalAny(info.Features)
+		if err != nil {
+			return nil, fmt.Errorf("failed to unmarshal RuntimeInfo.Features (%T): %w", info.Features, err)
+		}
+	}
+	result.Annotations = info.Annotations
+	return &result, nil
+}