e2e node: Update runtime class handler skip logic

There are two runtime class tests which required the container runtime
config to include explicit configuration for `test-handler`. The current
logic skips these tests in non GCE environments. This skip is too strict
since the test is skipped in node e2e environments and in other
environments such as kind, which support running the test and also
configure `test-handler`.

Instead of skipping based on provider, add a new function
`NodeSupportsPreconfiguredRuntimeClassHandler` which examines the
underlying container runtime config and checks if the config includes
`test-handler`. The check is a bit brittle since it assumes container
runtime config paths, but it is a net improvement over skipping the test
entirely on non GCE environments.

This results in the test working in the common test environments, namely
GCE kube-up, node e2e, and kind.

Signed-off-by: David Porter <david@porter.me>

test/e2e_node/runtimeclass_test.go

@@ -26,7 +26,7 @@ import (
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/kubernetes/pkg/kubelet/cm"
 	"k8s.io/kubernetes/test/e2e/framework"
-	e2enode "k8s.io/kubernetes/test/e2e/framework/node"
+	e2eruntimeclass "k8s.io/kubernetes/test/e2e/framework/node/runtimeclass"
 	e2epod "k8s.io/kubernetes/test/e2e/framework/pod"
 	imageutils "k8s.io/kubernetes/test/utils/image"
 	admissionapi "k8s.io/pod-security-admission/api"
@@ -106,7 +106,7 @@ var _ = SIGDescribe("Kubelet PodOverhead handling [LinuxOnly]", func() {
 					handler       string
 				)
 				ginkgo.By("Creating a RuntimeClass with Overhead definied", func() {
-					handler = e2enode.PreconfiguredRuntimeClassHandler
+					handler = e2eruntimeclass.PreconfiguredRuntimeClassHandler
 					rc := &nodev1.RuntimeClass{
 						ObjectMeta: metav1.ObjectMeta{Name: handler},
 						Handler:    handler,