Track AutoscalingRunnerSet updates with metadata.generation

The AutoscalingRunnerSet controller detected changes by hashing the spec
and the labels on every reconcile and comparing the result against the
actions.github.com/integrity-hash annotation it had written on a previous
pass. That is a hand-rolled version of something the API server already
does for us: it bumps metadata.generation on every spec write, and nothing
else. Recording that value in the status as ObservedGeneration gives the
same "has this changed since I last applied it" signal without recomputing
a hash, without an extra non-status write to the object, and with a value a
user can read and reason about.

updateStatus now takes the observed generation and patches it next to the
phase, returning early only when both are already what we want. When the
generation is ahead of the observed generation we move to Pending but
deliberately leave the observed generation where it is; it only catches up
at the end of a reconcile that actually applied the change, so a reconcile
that fails part way through is retried as pending rather than being
mistaken for settled.

The old code returned immediately after stamping the hash. That was needed
because stamping the annotation was itself a write to the object, so
continuing would have worked from a stale copy. Recording the generation
only touches the status subresource, which does not bump generation, so the
rest of the reconcile can run on the same object and apply the change in
the same pass instead of waiting for the next event.

One user-visible difference: the old hash covered Labels as well as Spec,
and metadata.generation does not move when only labels change. Editing just
a label on an AutoscalingRunnerSet no longer forces it through Pending.
Labels still propagate to the EphemeralRunnerSet; they simply no longer
count as an update that has to be applied.

Hash, ListenerSpecHash and RunnerSetSpecHash are removed. The latter two
already had no callers, and the first has none now.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

apis/actions.github.com/v1alpha1/autoscalingrunnerset_types.go

@@ -23,7 +23,6 @@ import (
 	"net/url"
 	"strings"
 
-	"github.com/actions/actions-runner-controller/hash"
 	"github.com/actions/actions-runner-controller/vault"
 	"golang.org/x/net/http/httpproxy"
 	corev1 "k8s.io/api/core/v1"
@@ -322,6 +321,10 @@ type HistogramMetric struct {
 type AutoscalingRunnerSetStatus struct {
 	// +optional
 	Phase AutoscalingRunnerSetPhase `json:"phase"`
+	// ObservedGeneration tracks the metadata.generation of this ARS at observation time,
+	// enabling detection of Pending phase when generation differs. Unset defaults to 0.
+	// +optional
+	ObservedGeneration int64 `json:"observedGeneration,omitempty"`
 }
 
 type AutoscalingRunnerSetPhase string
@@ -334,26 +337,6 @@ const (
 	AutoscalingRunnerSetPhaseOutdated AutoscalingRunnerSetPhase = "Outdated"
 )
 
-func (ars *AutoscalingRunnerSet) Hash() string {
-	type data struct {
-		Spec   *AutoscalingRunnerSetSpec
-		Labels map[string]string
-	}
-
-	d := &data{
-		Spec:   ars.Spec.DeepCopy(),
-		Labels: ars.Labels,
-	}
-
-	return hash.ComputeTemplateHash(d)
-}
-
-func (ars *AutoscalingRunnerSet) ListenerSpecHash() string {
-	arsSpec := ars.Spec.DeepCopy()
-	spec := arsSpec
-	return hash.ComputeTemplateHash(&spec)
-}
-
 func (ars *AutoscalingRunnerSet) GitHubConfigSecret() string {
 	return ars.Spec.GitHubConfigSecret
 }
@@ -381,28 +364,6 @@ func (ars *AutoscalingRunnerSet) VaultProxy() *ProxyConfig {
 	return nil
 }
 
-func (ars *AutoscalingRunnerSet) RunnerSetSpecHash() string {
-	type runnerSetSpec struct {
-		GitHubConfigUrl    string
-		GitHubConfigSecret string
-		RunnerGroup        string
-		RunnerScaleSetName string
-		Proxy              *ProxyConfig
-		GitHubServerTLS    *TLSConfig
-		Template           corev1.PodTemplateSpec
-	}
-	spec := &runnerSetSpec{
-		GitHubConfigUrl:    ars.Spec.GitHubConfigUrl,
-		GitHubConfigSecret: ars.Spec.GitHubConfigSecret,
-		RunnerGroup:        ars.Spec.RunnerGroup,
-		RunnerScaleSetName: ars.Spec.RunnerScaleSetName,
-		Proxy:              ars.Spec.Proxy,
-		GitHubServerTLS:    ars.Spec.GitHubServerTLS,
-		Template:           ars.Spec.Template,
-	}
-	return hash.ComputeTemplateHash(&spec)
-}
-
 // +kubebuilder:object:root=true
 
 // AutoscalingRunnerSetList contains a list of AutoscalingRunnerSet