Merge pull request #64097 from damemi/hpa-metrics-specificity

Automatic merge from submit-queue (batch tested with PRs 67894, 64097). If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.

HPA metrics specificity improvements

**What this PR does / why we need it**:
Improves available specificity for HPA metrics by adding metric selector fields for metrics of Pods and Objects. 

**Which issue(s) this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close the issue(s) when PR gets merged)*:
Implements this KEP: https://github.com/kubernetes/community/pull/2055

**Special notes for your reviewer**:
Need to add/update tests?

**Release note**:

```release-note
Introduces autoscaling/v2beta2 and custom_metrics/v1beta2, which implement metric selectors for Object and Pods metrics, as well as allowing AverageValue targets on Objects, similar to External metrics.
```

/assign @DirectXMan12

test/integration/etcd/etcd_storage_path_test.go

@@ -210,6 +210,14 @@ var etcdStorageData = map[schema.GroupVersionResource]struct {
 	},
 	// --
 
+	// k8s.io/kubernetes/pkg/apis/autoscaling/v2beta2
+	gvr("autoscaling", "v2beta2", "horizontalpodautoscalers"): {
+		stub:             `{"metadata": {"name": "hpa3"}, "spec": {"maxReplicas": 3, "scaleTargetRef": {"kind": "something", "name": "cross"}}}`,
+		expectedEtcdPath: "/registry/horizontalpodautoscalers/etcdstoragepathtestnamespace/hpa3",
+		expectedGVK:      gvkP("autoscaling", "v1", "HorizontalPodAutoscaler"),
+	},
+	// --
+
 	// k8s.io/kubernetes/pkg/apis/batch/v1
 	gvr("batch", "v1", "jobs"): {
 		stub:             `{"metadata": {"name": "job1"}, "spec": {"manualSelector": true, "selector": {"matchLabels": {"controller-uid": "uid1"}}, "template": {"metadata": {"labels": {"controller-uid": "uid1"}}, "spec": {"containers": [{"image": "fedora:latest", "name": "container1"}], "dnsPolicy": "ClusterFirst", "restartPolicy": "Never"}}}}`,