Add container monitor plugin type for restart

Adds a plugin type for container monitor.
Rename the task monitor type to avoid confusion.
Add config migration for new plugin types to pass existing migration
tests.

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

plugins/restart/monitor.go

@@ -28,6 +28,7 @@ import (
 	"github.com/containerd/containerd/v2/internal/tomlext"
 	"github.com/containerd/containerd/v2/pkg/namespaces"
 	"github.com/containerd/containerd/v2/plugins"
+	"github.com/containerd/containerd/v2/version"
 	"github.com/containerd/log"
 	"github.com/containerd/plugin"
 	"github.com/containerd/plugin/registry"
@@ -41,7 +42,7 @@ type Config struct {
 
 func init() {
 	registry.Register(&plugin.Registration{
-		Type: plugins.InternalPlugin,
+		Type: plugins.ContainerMonitorPlugin,
 		Requires: []plugin.Type{
 			plugins.EventPlugin,
 			plugins.ServicePlugin,
@@ -62,6 +63,19 @@ func init() {
 			go m.run(tomlext.ToStdTime(ic.Config.(*Config).Interval))
 			return m, nil
 		},
+		ConfigMigration: func(ctx context.Context, configVersion int, pluginConfigs map[string]interface{}) error {
+			if configVersion >= version.ConfigVersion {
+				return nil
+			}
+			const pluginName = string(plugins.InternalPlugin) + ".restart"
+			c, ok := pluginConfigs[pluginName]
+			if ok {
+				pluginConfigs[string(plugins.ContainerMonitorPlugin)+".restart"] = c
+				delete(pluginConfigs, pluginName)
+			}
+
+			return nil
+		},
 	})
 }