Add SeccompDefault feature

This adds the gate `SeccompDefault` as new alpha feature. Seccomp path
and field fallbacks are now passed to the helper functions, whereas unit
tests covering those code paths have been added as well.

Beside enabling the feature gate, the feature has to be enabled by the
`SeccompDefault` kubelet configuration or its corresponding
`--seccomp-default` CLI flag.

Signed-off-by: Sascha Grunert <sgrunert@redhat.com>

Apply suggestions from code review

Co-authored-by: Paulo Gomes <pjbgf@linux.com>
Signed-off-by: Sascha Grunert <sgrunert@redhat.com>

pkg/kubelet/kubelet.go

@@ -367,7 +367,9 @@ func NewMainKubelet(kubeCfg *kubeletconfiginternal.KubeletConfiguration,
 	keepTerminatedPodVolumes bool,
 	nodeLabels map[string]string,
 	seccompProfileRoot string,
-	nodeStatusMaxImages int32) (*Kubelet, error) {
+	nodeStatusMaxImages int32,
+	seccompDefault bool,
+) (*Kubelet, error) {
 	if rootDirectory == "" {
 		return nil, fmt.Errorf("invalid root directory %q", rootDirectory)
 	}
@@ -649,6 +651,7 @@ func NewMainKubelet(kubeCfg *kubeletconfiginternal.KubeletConfiguration,
 		kubeDeps.dockerLegacyService,
 		klet.containerLogManager,
 		klet.runtimeClassManager,
+		seccompDefault,
 	)
 	if err != nil {
 		return nil, err