Adding direct-to-KubeRay path for the SDK

[Maxusmusti]

Name of Feature or Improvement

Adding KubeRay direct support to the SDK

Description of Problem the Feature Should Solve

For users who wish to use the SDK as a direct interface with KubeRay, mainly around single-user experimentation and new Kubernetes users approaching the stack for the first time

Describe the Solution You Would Like to See

Adding an optional path for creating direct RayCluster objects and associated resources, in addition to current AppWrapper generation

Additional Context

Feature requested by new users from Ray Summit and other Kubernetes/KubeRay communities