What type of PR is this?

/kind feature

What this PR does / why we need it:

This PR implements KEP-4680 by adding device health tracking for DRA plugins and integrating this status into the PodStatus. It allows Kubelet and users to observe the health of allocated DRA resources.

1. Optional gRPC Health Service (dra-health/v1alpha1):

   • Defines a new NodeHealthService with a WatchResources stream RPC in staging/src/k8s.io/kubelet/pkg/apis/dra-health/v1alpha1/api.proto.
   • DRA plugins can optionally implement this service to stream device health updates (pool_name, device_name, health, Last_updated) to Kubelet.

2. Kubelet Plugin Integration (cm/dra/plugin):

   • RegistrationHandler (registration.go) updated to:
     • Attempt to start the WatchResources stream upon plugin registration via plugin.WatchResources.
     • Handle plugins that don't implement the NodeHealthService (or other stream startup errors) by logging the error and proceeding with registration without health monitoring.
     • Launch a handler goroutine (via StreamHandler interface implemented by dra.ManagerImpl) in the DRA Manager upon successful stream initiation.
     • Cancel the health stream context (HealthStreamCancel) during plugin deregistration (DeregisterPlugin) or replacement.

3. Health Cache (cm/dra/healthinfo.go, cm/dra/state/state.go):

   • Implements healthInfoCache for persistent (dra_health_state file), thread-safe storage of device health (Healthy, Unhealthy, Unknown) and timestamps.
   • Includes updateHealthInfo for full-state reconciliation based on plugin updates, handling timeouts (healthTimeout constant, e.g., 30s) by marking stale devices as "Unknown". Saves checkpoint on change.
   • Includes getHealthInfo to retrieve current status (returns "Unknown" if stale/missing) and clearDriver for cleanup.

4. DRA Manager Integration (cm/dra/manager.go):

   • ManagerImpl implements the plugin.StreamHandler interface.
   • HandleWatchResourcesStream goroutine consumes updates from the plugin stream (NodeHealth.WatchResourcesClient), calls healthInfoCache.updateHealthInfo, finds affected Pod UIDs from claimInfoCache, and sends notifications via an internal update channel (non-blocking).
   • Added defer healthInfoCache.clearDriver(pluginName) within HandleWatchResourcesStream to ensure cache cleanup for the driver upon goroutine exit (due to error, cancellation, or EOF).
   • Adds Updates() method to return the update channel.
   • Updates UpdateAllocatedResourcesStatus to read health from healthInfoCache and populate pod.Status.ContainerStatuses[].AllocatedResourcesStatus using the KEP-specified structure: v1.ResourceStatus (named by claim (Name field), containing a Resources slice where each element is a v1.ResourceHealth struct per device (ResourceID and Health fields)).

5. Container Manager Integration (cm/container_manager_linux.go):

   • Updates() method merges update signals from Device Manager and DRA Manager (via draManager.Updates()).
   • UpdateAllocatedResourcesStatus() method calls both Device Manager and DRA Manager update functions (DRA call guarded by feature gate DynamicResourceAllocation and nil check).

6. Testing:

   • Adds unit tests for healthinfo.go (healthinfo_test.go).
   • Adds unit tests for manager.go (manager_test.go) covering HandleWatchResourcesStream and UpdateAllocatedResourcesStatus. Fixes existing tests (TestPrepareResources, TestUnprepareResources) to align with updated signatures/logic.
   • WIP E2E Test

Which issue(s) this PR fixes:

Fixes #126243

Special notes for your reviewer:

Does this PR introduce a user-facing change?

Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.:

- [KEP]: https://github.com/kubernetes/enhancements/blob/master/keps/sig-node/4680-add-resource-health-to-pod-status/README.md