DRA: add DRAControlPlaneController feature gate for "classic DRA"

In the API, the effect of the feature gate is that alpha fields get dropped on
create. They get preserved during updates if already set. The
PodSchedulingContext registration is *not* restricted by the feature gate.
This enables deleting stale PodSchedulingContext objects after disabling
the feature gate.

The scheduler checks the new feature gate before setting up an informer for
PodSchedulingContext objects and when deciding whether it can schedule a
pod. If any claim depends on a control plane controller, the scheduler bails
out, leading to:

    Status:       Pending
    ...
      Warning  FailedScheduling             73s   default-scheduler  0/1 nodes are available: resourceclaim depends on disabled DRAControlPlaneController feature. no new claims to deallocate, preemption: 0/1 nodes are available: 1 Preemption is not helpful for scheduling.

The rest of the changes prepare for testing the new feature separately from
"structured parameters". The goal is to have base "dra" jobs which just enable
and test those, then "classic-dra" jobs which add DRAControlPlaneController.

pkg/scheduler/framework/plugins/dynamicresources/dynamicresources_test.go

@@ -316,7 +316,11 @@ func TestPlugin(t *testing.T) {
 
 		prepare prepare
 		want    want
-		disable bool
+
+		// Feature gates. False is chosen so that the uncommon case
+		// doesn't need to be set.
+		disableDRA        bool
+		disableClassicDRA bool
 	}{
 		"empty": {
 			pod: st.MakePod().Name("foo").Namespace("default").Obj(),
@@ -912,7 +916,7 @@ func TestPlugin(t *testing.T) {
 			pod:    podWithClaimName,
 			claims: []*resourceapi.ResourceClaim{inUseClaim},
 		},
-		"disable": {
+		"DRA-disabled": {
 			pod:    podWithClaimName,
 			claims: []*resourceapi.ResourceClaim{inUseClaim},
 			want: want{
@@ -920,7 +924,7 @@ func TestPlugin(t *testing.T) {
 					status: framework.NewStatus(framework.Skip),
 				},
 			},
-			disable: true,
+			disableDRA: true,
 		},
 	}
 
@@ -933,8 +937,11 @@ func TestPlugin(t *testing.T) {
 			if nodes == nil {
 				nodes = []*v1.Node{workerNode}
 			}
-			testCtx := setup(t, nodes, tc.claims, tc.classes, tc.schedulings, tc.objs)
-			testCtx.p.enabled = !tc.disable
+			features := feature.Features{
+				EnableDynamicResourceAllocation: !tc.disableDRA,
+				EnableDRAControlPlaneController: !tc.disableClassicDRA,
+			}
+			testCtx := setup(t, nodes, tc.claims, tc.classes, tc.schedulings, tc.objs, features)
 			initialObjects := testCtx.listAll(t)
 
 			status := testCtx.p.PreEnqueue(testCtx.ctx, tc.pod)
@@ -1136,6 +1143,9 @@ func (tc *testContext) listAll(t *testing.T) (objects []metav1.Object) {
 }
 
 func (tc *testContext) listAssumedClaims() []metav1.Object {
+	if tc.p.claimAssumeCache == nil {
+		return nil
+	}
 	var assumedClaims []metav1.Object
 	for _, obj := range tc.p.claimAssumeCache.List(nil) {
 		claim := obj.(*resourceapi.ResourceClaim)
@@ -1219,7 +1229,7 @@ func update(t *testing.T, objects []metav1.Object, updates change) []metav1.Obje
 	return updated
 }
 
-func setup(t *testing.T, nodes []*v1.Node, claims []*resourceapi.ResourceClaim, classes []*resourceapi.DeviceClass, schedulings []*resourceapi.PodSchedulingContext, objs []apiruntime.Object) (result *testContext) {
+func setup(t *testing.T, nodes []*v1.Node, claims []*resourceapi.ResourceClaim, classes []*resourceapi.DeviceClass, schedulings []*resourceapi.PodSchedulingContext, objs []apiruntime.Object, features feature.Features) (result *testContext) {
 	t.Helper()
 
 	tc := &testContext{}
@@ -1242,7 +1252,7 @@ func setup(t *testing.T, nodes []*v1.Node, claims []*resourceapi.ResourceClaim,
 		t.Fatal(err)
 	}
 
-	pl, err := New(tCtx, nil, fh, feature.Features{EnableDynamicResourceAllocation: true})
+	pl, err := New(tCtx, nil, fh, features)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -1436,7 +1446,10 @@ func Test_isSchedulableAfterClaimChange(t *testing.T) {
 	for name, tc := range testcases {
 		t.Run(name, func(t *testing.T) {
 			logger, tCtx := ktesting.NewTestContext(t)
-			testCtx := setup(t, nil, tc.claims, nil, nil, nil)
+			features := feature.Features{
+				EnableDynamicResourceAllocation: true,
+			}
+			testCtx := setup(t, nil, tc.claims, nil, nil, nil, features)
 			oldObj := tc.oldObj
 			newObj := tc.newObj
 			if claim, ok := tc.newObj.(*resourceapi.ResourceClaim); ok {
@@ -1604,7 +1617,11 @@ func Test_isSchedulableAfterPodSchedulingContextChange(t *testing.T) {
 		t.Run(name, func(t *testing.T) {
 			t.Parallel()
 			logger, _ := ktesting.NewTestContext(t)
-			testCtx := setup(t, nil, tc.claims, nil, tc.schedulings, nil)
+			features := feature.Features{
+				EnableDynamicResourceAllocation: true,
+				EnableDRAControlPlaneController: true,
+			}
+			testCtx := setup(t, nil, tc.claims, nil, tc.schedulings, nil, features)
 			actualHint, err := testCtx.p.isSchedulableAfterPodSchedulingContextChange(logger, tc.pod, tc.oldObj, tc.newObj)
 			if tc.expectedErr {
 				require.Error(t, err)