Cleanup introspection interface

Split service proxy from service plugin.
Make introspection service easier for clients to use.
Update service proxy to support grpc and ttrpc.

Signed-off-by: Derek McGowan <derek@mcg.dev>

cmd/ctr/commands/client.go

@@ -24,7 +24,6 @@ import (
 	containerd "github.com/containerd/containerd/v2/client"
 	"github.com/containerd/containerd/v2/pkg/epoch"
 	"github.com/containerd/containerd/v2/pkg/namespaces"
-	ptypes "github.com/containerd/containerd/v2/protobuf/types"
 	"github.com/containerd/log"
 	"github.com/urfave/cli/v2"
 )
@@ -73,7 +72,7 @@ func NewClient(context *cli.Context, opts ...containerd.Opt) (*containerd.Client
 		}
 	}
 	if !suppressDeprecationWarnings {
-		resp, err := client.IntrospectionService().Server(ctx, &ptypes.Empty{})
+		resp, err := client.IntrospectionService().Server(ctx)
 		if err != nil {
 			log.L.WithError(err).Warn("Failed to check deprecations")
 		} else {

cmd/ctr/commands/deprecations/deprecations.go

@@ -27,7 +27,6 @@ import (
 	api "github.com/containerd/containerd/v2/api/services/introspection/v1"
 	"github.com/containerd/containerd/v2/cmd/ctr/commands"
 	"github.com/containerd/containerd/v2/protobuf"
-	ptypes "github.com/containerd/containerd/v2/protobuf/types"
 )
 
 // Command is the parent for all commands under "deprecations"
@@ -56,7 +55,7 @@ var listCommand = &cli.Command{
 		}
 		defer cancel()
 
-		resp, err := client.IntrospectionService().Server(ctx, &ptypes.Empty{})
+		resp, err := client.IntrospectionService().Server(ctx)
 		if err != nil {
 			return err
 		}

cmd/ctr/commands/info/info.go

@@ -19,7 +19,6 @@ package info
 import (
 	api "github.com/containerd/containerd/v2/api/services/introspection/v1"
 	"github.com/containerd/containerd/v2/cmd/ctr/commands"
-	ptypes "github.com/containerd/containerd/v2/protobuf/types"
 	"github.com/urfave/cli/v2"
 )
 
@@ -38,7 +37,7 @@ var Command = &cli.Command{
 		}
 		defer cancel()
 		var info Info
-		info.Server, err = client.IntrospectionService().Server(ctx, &ptypes.Empty{})
+		info.Server, err = client.IntrospectionService().Server(ctx)
 		if err != nil {
 			return err
 		}

cmd/ctr/commands/plugins/plugins.go

@@ -71,7 +71,7 @@ var listCommand = &cli.Command{
 		}
 		defer cancel()
 		ps := client.IntrospectionService()
-		response, err := ps.Plugins(ctx, context.Args().Slice())
+		response, err := ps.Plugins(ctx, context.Args().Slice()...)
 		if err != nil {
 			return err
 		}