Support scale subresource to scale Runners with kubectl

[duhow]

Is your feature request related to a problem? Please describe. According to https://kubernetes.io/docs/tasks/extend-kubernetes/custom-resources/custom-resource-definitions/#subresources :

Custom resources support /status and /scale subresources. The status and scale subresources can be optionally enabled by defining them in the CustomResourceDefinition.

Describe the solution you'd like Being able to scale RunnerDeployments, RunnerStatefulSets and/or RunnerReplicaSets with kubectl:

kubectl scale rdeploy github-runner --replicas=4

Additional context https://github.com/actions-runner-controller/actions-runner-controller/blob/538e2783d7fde279b84f1ff9351bb1486823660b/charts/actions-runner-controller/crds/actions.summerwind.dev_runnerdeployments.yaml#L5256-L5257