[InferenceModel update] Slim down InferenceObjectives/InferenceModel API

[kfswain]

Related to: https://github.com/kubernetes-sigs/gateway-api-inference-extension/tree/main/docs/proposals/1199-inferencemodel-api-evolution#structure-change

The InferenceModel/InferenceObjectives API will remove many of the old InferenceModels field to mirror: https://github.com/kubernetes-sigs/gateway-api-inference-extension/tree/main/docs/proposals/1199-inferencemodel-api-evolution#structure-change

[nirrozenbaum]

can we close this issue as done?

[kfswain]

I'll be cutting the Criticality PR shortly and it will be the last remaining item (apart from documentation), I'll mark this as fixed in that PR