De-share the Handler struct in core API (#105979)

* De-share the Handler struct in core API

An upcoming PR adds a handler that only applies on one of these paths.
Having fields that don't work seems bad.

This never should have been shared.  Lifecycle hooks are like a "write"
while probes are more like a "read". HTTPGet and TCPSocket don't really
make sense as lifecycle hooks (but I can't take that back). When we add
gRPC, it is EXPLICITLY a health check (defined by gRPC) not an arbitrary
RPC - so a probe makes sense but a hook does not.

In the future I can also see adding lifecycle hooks that don't make
sense as probes.  E.g. 'sleep' is a common lifecycle request. The only
option is `exec`, which requires having a sleep binary in your image.

* Run update scripts

pkg/kubelet/kuberuntime/labels_test.go

@@ -20,7 +20,7 @@ import (
 	"reflect"
 	"testing"
 
-	"k8s.io/api/core/v1"
+	v1 "k8s.io/api/core/v1"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/util/intstr"
 	kubecontainer "k8s.io/kubernetes/pkg/kubelet/container"
@@ -31,7 +31,7 @@ func TestContainerLabels(t *testing.T) {
 	terminationGracePeriod := int64(10)
 	lifecycle := &v1.Lifecycle{
 		// Left PostStart as nil
-		PreStop: &v1.Handler{
+		PreStop: &v1.LifecycleHandler{
 			Exec: &v1.ExecAction{
 				Command: []string{"action1", "action2"},
 			},
@@ -100,7 +100,7 @@ func TestContainerAnnotations(t *testing.T) {
 	}
 	lifecycle := &v1.Lifecycle{
 		// Left PostStart as nil
-		PreStop: &v1.Handler{
+		PreStop: &v1.LifecycleHandler{
 			Exec: &v1.ExecAction{
 				Command: []string{"action1", "action2"},
 			},