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>

integration/client/client_test.go

@@ -24,11 +24,13 @@ import (
 	"io"
 	"os"
 	"os/exec"
+	"runtime"
 	"testing"
 	"time"
 
 	"github.com/opencontainers/go-digest"
 	"github.com/opencontainers/image-spec/identity"
+	"github.com/opencontainers/runtime-spec/specs-go/features"
 	"github.com/stretchr/testify/require"
 	"go.opentelemetry.io/otel"
 
@@ -546,3 +548,46 @@ func TestDefaultRuntimeWithNamespaceLabels(t *testing.T) {
 		t.Error("failed to set default runtime from namespace labels")
 	}
 }
+
+func TestRuntimeInfo(t *testing.T) {
+	t.Parallel()
+
+	if runtime.GOOS == "windows" {
+		t.Skip("io.containerd.runhcs.v1 does not implement `containerd-shim-runhcs-v1.exe -info` yet")
+	}
+
+	client, err := newClient(t, address)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer client.Close()
+
+	ctx, cancel := testContext(t)
+	defer cancel()
+
+	rti, err := client.RuntimeInfo(ctx, "", nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if rti.Name == "" {
+		t.Fatal("got empty RuntimeInfo.Name")
+	}
+
+	feat, ok := rti.Features.(*features.Features)
+	if !ok {
+		t.Fatalf("expected RuntimeInfo.Features to be *features.Features, got %T", rti.Features)
+	}
+
+	var rroRecognized bool
+	for _, f := range feat.MountOptions {
+		// "rro" is recognized since runc v1.1.
+		// The functionality needs kernel >= 5.12, but `runc features` consistently include "rro" in feat.MountOptions.
+		if f == "rro" {
+			rroRecognized = true
+		}
+	}
+	if !rroRecognized {
+		t.Fatalf("expected feat.MountOptions to contain \"rro\", only got %v", feat.MountOptions)
+	}
+}