generic ephemeral volume: graduation to GA

The feature gate gets locked to "true", with the goal to remove it in two
releases.

All code now can assume that the feature is enabled. Tests for "feature
disabled" are no longer needed and get removed.

Some code wasn't using the new helper functions yet. That gets changed while
touching those lines.

pkg/api/pod/util.go

@@ -556,7 +556,6 @@ func dropDisabledFields(
 	dropDisabledProcMountField(podSpec, oldPodSpec)
 
 	dropDisabledCSIVolumeSourceAlphaFields(podSpec, oldPodSpec)
-	dropDisabledEphemeralVolumeSourceAlphaFields(podSpec, oldPodSpec)
 
 	if !utilfeature.DefaultFeatureGate.Enabled(features.NonPreemptingPriority) &&
 		!podPriorityInUse(oldPodSpec) {
@@ -605,16 +604,6 @@ func dropDisabledCSIVolumeSourceAlphaFields(podSpec, oldPodSpec *api.PodSpec) {
 	}
 }
 
-// dropDisabledEphemeralVolumeSourceAlphaFields removes disabled alpha fields from []EphemeralVolumeSource.
-// This should be called from PrepareForCreate/PrepareForUpdate for all pod specs resources containing a EphemeralVolumeSource
-func dropDisabledEphemeralVolumeSourceAlphaFields(podSpec, oldPodSpec *api.PodSpec) {
-	if !utilfeature.DefaultFeatureGate.Enabled(features.GenericEphemeralVolume) && !ephemeralInUse(oldPodSpec) {
-		for i := range podSpec.Volumes {
-			podSpec.Volumes[i].Ephemeral = nil
-		}
-	}
-}
-
 func dropPodAffinityTermNamespaceSelector(terms []api.PodAffinityTerm) {
 	for i := range terms {
 		terms[i].NamespaceSelector = nil
@@ -795,19 +784,6 @@ func csiInUse(podSpec *api.PodSpec) bool {
 	return false
 }
 
-// ephemeralInUse returns true if any pod's spec include inline CSI volumes.
-func ephemeralInUse(podSpec *api.PodSpec) bool {
-	if podSpec == nil {
-		return false
-	}
-	for i := range podSpec.Volumes {
-		if podSpec.Volumes[i].Ephemeral != nil {
-			return true
-		}
-	}
-	return false
-}
-
 // SeccompAnnotationForField takes a pod seccomp profile field and returns the
 // converted annotation value
 func SeccompAnnotationForField(field *api.SeccompProfile) string {