Implement PodSet inference for LeaderWorkerSet

[dgrove-oss]

Name of Feature or Improvement

Implement PodSet inference for leaderworkerset.x-k8s.io/leaderworkerset.

Description of Problem the Feature Should Solve

This would simplify the user experience for wrapping LeaderWorkSets in AppWrappers by allowing the
user to omit the explicit podSets information.

Describe the Solution You Would Like to See

The implementation would be to add an additional case to utils.InferPodSets to handle LeaderWorkerSet.