Implement KubeletPluginBuilder — configuration, start, and stop lifecycle

[gauravgahlot]

Equivalent to Go's options struct, Helper struct, and Start function. This is the main
entry point for library users. The builder should accept all the configuration knobs the Go
library exposes: driver name, kube client, node name, node UID, registrar directory, plugin
data directory, socket names, rolling update UID, serialization toggle, flock directory, and
individual toggles for the DRA and registration services. The start method validates required
fields, enforces mutual exclusion between rolling update UID and an explicit registrar socket
name, applies defaults, starts both gRPC servers, and returns a KubeletPlugin handle. stop
cancels all background tasks and waits for them to finish.

References

• Go options struct: https://github.com/kubernetes/dynamic-resource-allocation/blob/main/kubeletplugin/draplugin.go#L476-L497
• Go Helper struct: https://github.com/kubernetes/dynamic-resource-allocation/blob/main/kubeletplugin/draplugin.go#L499-L524
• Go Start function: https://github.com/kubernetes/dynamic-resource-allocation/blob/main/kubeletplugin/draplugin.go#L537-L718
• Go Stop: https://github.com/kubernetes/dynamic-resource-allocation/blob/main/kubeletplugin/draplugin.go#L721-L728
• Rolling update design (k8s 1.33+): https://kubernetes.io/docs/concepts/scheduling-eviction/dynamic-resource-allocation/#running-the-kubelet-plugin
• tokio-util CancellationToken: https://docs.rs/tokio-util/latest/tokio_util/sync/struct.CancellationToken.html