[Feature] Use image of Ray head container as the default Ray Autoscaler container

[kevin85421]

Why are these changes needed?

Before the introduction of this PR, KubeRay used to determine the Ray Autoscaler sidecar container's image based on the rayVersion parameter.

• Case 1: If this version was older than Ray 2.0.0, KubeRay defaulted to using Ray 2.0.0 for the sidecar container image.
• Case 2: In other cases, it used the same image as the Ray head container. For more information, please refer to autoscalerSupportIsStable and getAutoscalerImage.

Case 1 is not necessary at this moment because KubeRay does not guarantee the support of a version older than Ray 2.0.0. In addition, there is no compatibility test for the version mismatch between Ray Autoscaler and Ray.

I also removed the description of the rayVersion behavior in ray-project/ray#39345.

Related issue number

Checks

• I've made sure the tests are passing.
• Testing Strategy
  • Unit tests
  • Manual tests (I can reproduce [KubeRay][Doc] KubeRay doc migration (3/n) ray#39345.)
  • This PR is not tested :(

[architkulkarni]

The code looks good, but doesn't KubeRay guarantee compatibility with the last Ray 1.x version?

[kevin85421]

The code looks good, but doesn't KubeRay guarantee compatibility with the last Ray 1.x version?

Yes, KubeRay offers compatibility with Ray 1.13.0 for certain features. However, the compatibility mentioned above involves using Ray 1.x for the Ray container and Ray 2.0.0 for the Ray Autoscaler sidecar container. If I recall correctly, no one has yet tested or tried this combination.

[architkulkarni]

Makes sense, thanks!