Introduce keepFailedPods to cleanup failed pods

We're using the spacelift-workerpool-controller Helm chart and managing our WorkerPools via the provided CRDs. We've noticed that while the keepSuccessfulPods option is available to manage successful pod cleanup, there doesn't seem to be a similar option for failed pods.

We understand that keeping failed pods is useful for debugging purposes. However, over time this can clutter the namespace and create additional maintenance overhead. While we could implement our own cleanup mechanism, we wanted to reach out and ask if there's an existing way to handle this - or if you'd consider introducing a keepFailedPods option to provide more flexibility.

Thanks in advance for the help!