Workload Aware Scheduling Controller APIs

This KEP proposes a standardized set of reusable API building blocks (scheduling.k8s.io), integration guidelines, and shared libraries to simplify how workload controllers (e.g., JobSet, TrainJob, RayJob, LWS, SparkApplication, as well as core workloads like Job, Deployment, and StatefulSet) integrate with Workload-aware Scheduling (WAS). In v1.37, this KEP and the reusable building blocks entered Alpha alongside the core Job integration ([KEP-5547]). For v1.38, this KEP is promoted to Beta. To support embedding into GA v1 workload APIs (batch/v1, apps/v1), the reusable building block structs graduate directly into scheduling.k8s.io/v1 (with Go type aliases maintained in scheduling.k8s.io/v1alpha3 for backward compatibility), formalizing stable primitives for the entire Kubernetes ecosystem. By providing common API primitives (such as topology constraints and disruption policies) and a shared library (workloadbuilder) to handle boilerplate resource generation, we enable controller developers to easily expose WAS features natively within their APIs without reinventing the wheel, while ensuring a consistent user experience across the Kubernetes ecosystem.