autoscaler: populate status, conditions, and observedGeneration for homogeneous and heterogeneous policies

[bhuvan-somisetty]

What type of PR is this?

/kind bug

What this PR does / why we need it:

AutoscaleController previously only updated AutoscalingPolicy custom resource status for DisaggregatedTarget policies (via updateDisaggregatedPolicyStatus). For HomogeneousTarget and HeterogeneousTarget policies, doScale and doOptimize executed the replica scaling patches on ModelServing instances but omitted updating .status on the AutoscalingPolicy custom resource entirely.

As a result, AutoscalingPolicy resources using homogeneous or heterogeneous scaling targets remained with empty status blocks (status: {}), leaving observedGeneration, conditions (Ready, TargetFound), homogeneousStatus, and heterogeneousStatus unpopulated.

This PR adds status update helpers and integrates them into doScale and doOptimize:

• updateHomogeneousPolicyStatus: Writes ObservedGeneration, Conditions (Ready, TargetFound), and HomogeneousStatus (current/desired replicas, mode, last scale time).
• updateHeterogeneousPolicyStatus: Writes ObservedGeneration, Conditions (Ready, TargetFound), and HeterogeneousStatus (per-target current/desired replicas, mode, last scale time).
• Employs retry.RetryOnConflict with a fallback API read strategy to handle status update conflicts cleanly.

Which issue(s) this PR fixes:
Fixes #1469

Bug evidence (required for bug-related PRs):

Source path inspection:

• doScale in pkg/autoscaler/controller/autoscale_controller.go scaled target replicas but had no status update call.
• doOptimize in pkg/autoscaler/controller/autoscale_controller.go scaled target replicas across heterogeneous backends but had no status update call.
• AutoscalingPolicyStatus API definition in pkg/apis/workload/v1alpha1/autoscalingpolicy_types.go explicitly defines HomogeneousStatus and HeterogeneousStatus, but no corresponding status reconciliation functions existed in AutoscaleController.

Reproduction:

1. Apply an AutoscalingPolicy with a homogeneousTarget or heterogeneousTarget.
2. Observe that AutoscaleController reconciles and scales target ModelServing instances.
3. Check kubectl get asp <name> -o yaml — .status is completely empty.

Special notes for your reviewer:

• Comprehensive unit tests added in pkg/autoscaler/controller/autoscale_controller_test.go:
  • TestUpdateHomogeneousPolicyStatus_Success
  • TestUpdateHomogeneousPolicyStatus_TargetNotFound
  • TestUpdateHeterogeneousPolicyStatus_Success
  • TestUpdateHeterogeneousPolicyStatus_TargetNotFound
• All 21 tests in pkg/autoscaler/controller pass cleanly.

Does this PR introduce a user-facing change?:

Fix AutoscaleController to populate status, conditions, and observedGeneration for HomogeneousTarget and HeterogeneousTarget AutoscalingPolicies.

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[bhuvan-somisetty]

/cc @YaoZengzeng @LiZhenCheng9527 @hzxuzhonghu @git-malu

This PR resolves issue #1469 by implementing status update helpers (updateHomogeneousPolicyStatus and updateHeterogeneousPolicyStatus) for HomogeneousTarget and HeterogeneousTarget policies in AutoscaleController. It ensures .status (ObservedGeneration, Conditions, HomogeneousStatus, HeterogeneousStatus) is accurately populated and updated with conflict retry handling.

[bhuvan-somisetty]

cc @YaoZengzeng @LiZhenCheng9527 @hzxuzhonghu @git-malu @FAUST-BENCHOU

Hello maintainers, when you get a chance please take a look at this PR. It populates status fields (ObservedGeneration, Conditions, HomogeneousStatus, and HeterogeneousStatus) for homogeneous and heterogeneous autoscaling policies so their status is no longer left empty in production. All tests are passing.

[bhuvan-somisetty]

hi @LiZhenCheng9527 PTAL , whenever u get chance