CRI: Make stats respect sandbox's platform

To further some ongoing work in containerd to make as much code as possible
able to be used on any platform (to handle runtimes that can virtualize/emulate
a variety of different OSes), this change makes stats able to be handled on
any of the supported stat types (just linux and windows). To accomplish this,
we use the platform the sandbox returns from its `Platform` rpc to decide
what format the containers in a given sandbox are returning metrics in, then
we can typecast/marshal accordingly.

Signed-off-by: Danny Canter <danny@dcantah.dev>

pkg/cri/sbserver/container_stats.go

@@ -40,7 +40,12 @@ func (c *criService) ContainerStats(ctx context.Context, in *runtime.ContainerSt
 		return nil, fmt.Errorf("unexpected metrics response: %+v", resp.Metrics)
 	}
 
-	cs, err := c.containerMetrics(cntr.Metadata, resp.Metrics[0])
+	handler, err := c.getMetricsHandler(ctx, cntr.SandboxID)
+	if err != nil {
+		return nil, err
+	}
+
+	cs, err := handler(cntr.Metadata, resp.Metrics[0])
 	if err != nil {
 		return nil, fmt.Errorf("failed to decode container metrics: %w", err)
 	}