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

Kubernetes-commit: fdb5707194d56cbbd0da11c5be3a2a5653e714c9

vendor/k8s.io/api/autoscaling/v2beta1/generated.proto

@@ -186,6 +186,7 @@ message HorizontalPodAutoscalerStatus {
   optional int32 desiredReplicas = 4;
 
   // currentMetrics is the last read state of the metrics used by this autoscaler.
+  // +optional
   repeated MetricStatus currentMetrics = 5;
 
   // conditions is the set of conditions required for this autoscaler to scale its target,
@@ -273,6 +274,17 @@ message ObjectMetricSource {
 
   // targetValue is the target value of the metric (as a quantity).
   optional k8s.io.apimachinery.pkg.api.resource.Quantity targetValue = 3;
+
+  // selector is the string-encoded form of a standard kubernetes label selector for the given metric
+  // When set, it is passed as an additional parameter to the metrics server for more specific metrics scoping
+  // When unset, just the metricName will be used to gather metrics.
+  // +optional
+  optional k8s.io.apimachinery.pkg.apis.meta.v1.LabelSelector selector = 4;
+
+  // averageValue is the target value of the average of the
+  // metric across all relevant pods (as a quantity)
+  // +optional
+  optional k8s.io.apimachinery.pkg.api.resource.Quantity averageValue = 5;
 }
 
 // ObjectMetricStatus indicates the current value of a metric describing a
@@ -286,6 +298,17 @@ message ObjectMetricStatus {
 
   // currentValue is the current value of the metric (as a quantity).
   optional k8s.io.apimachinery.pkg.api.resource.Quantity currentValue = 3;
+
+  // selector is the string-encoded form of a standard kubernetes label selector for the given metric
+  // When set in the ObjectMetricSource, it is passed as an additional parameter to the metrics server for more specific metrics scoping.
+  // When unset, just the metricName will be used to gather metrics.
+  // +optional
+  optional k8s.io.apimachinery.pkg.apis.meta.v1.LabelSelector selector = 4;
+
+  // averageValue is the current value of the average of the
+  // metric across all relevant pods (as a quantity)
+  // +optional
+  optional k8s.io.apimachinery.pkg.api.resource.Quantity averageValue = 5;
 }
 
 // PodsMetricSource indicates how to scale on a metric describing each pod in
@@ -299,6 +322,12 @@ message PodsMetricSource {
   // targetAverageValue is the target value of the average of the
   // metric across all relevant pods (as a quantity)
   optional k8s.io.apimachinery.pkg.api.resource.Quantity targetAverageValue = 2;
+
+  // selector is the string-encoded form of a standard kubernetes label selector for the given metric
+  // When set, it is passed as an additional parameter to the metrics server for more specific metrics scoping
+  // When unset, just the metricName will be used to gather metrics.
+  // +optional
+  optional k8s.io.apimachinery.pkg.apis.meta.v1.LabelSelector selector = 3;
 }
 
 // PodsMetricStatus indicates the current value of a metric describing each pod in
@@ -310,6 +339,12 @@ message PodsMetricStatus {
   // currentAverageValue is the current value of the average of the
   // metric across all relevant pods (as a quantity)
   optional k8s.io.apimachinery.pkg.api.resource.Quantity currentAverageValue = 2;
+
+  // selector is the string-encoded form of a standard kubernetes label selector for the given metric
+  // When set in the PodsMetricSource, it is passed as an additional parameter to the metrics server for more specific metrics scoping.
+  // When unset, just the metricName will be used to gather metrics.
+  // +optional
+  optional k8s.io.apimachinery.pkg.apis.meta.v1.LabelSelector selector = 3;
 }
 
 // ResourceMetricSource indicates how to scale on a resource metric known to