Make ModelName immutable

[ahg-g]

What would you like to be added:

Make ModelName in InferenceModel immutable.

While we can't do this using CEL, we can add ValidatingAdmissionPolicy as part of the CRD installation.

Why is this needed:

ModelName for a specific InferenceModel should not change. We had to add ModelName as a separate parameter instead of using the object name because the model name can be arbitrary and more flexible than k8s object names.

[hzxuzhonghu]

https://kubernetes.io/blog/2022/09/29/enforce-immutability-using-cel/#immutablility-after-first-modification It is possible with cel

[hzxuzhonghu]

/assign