feat(api): Introduce OptimizationJob v1alpha1 API Types and CEL Validation Rules (KEP-3562)

[Haseebx162006]

What this PR does / why we need it

This PR introduces the initial v1alpha1 API types and validation framework for OptimizationJob, as part of KEP-3562.

The API provides the foundational Kubernetes types required to represent hyperparameter optimization jobs in Kubeflow Trainer, including objectives, search algorithms, search spaces, parameters, and optimization results.

Proposed Changes

• Added OptimizationJob and OptimizationJobList API types.
• Added OptimizationJobSpec and OptimizationJobStatus.
• Added objective and optimization result types.
• Added Random and Grid search algorithm types.
• Added Uniform, LogUniform, and Categorical search-space types.
• Added parameter definitions and numeric bounds.
• Added CEL validation rules for search algorithms, search spaces, and parameter bounds.
• Registered OptimizationJob and OptimizationJobList with the v1alpha1 API scheme.
• Added unit tests covering JSON serialization and DeepCopy() behavior.

These types provide the API foundation for the OptimizationJob controller and subsequent optimization/suggestion-service integration described in KEP-3562.

Testing

• go test -v ./pkg/apis/trainer/v1alpha1/...

Which issue(s) this PR relates to

Part of #3562
Related to #3749

Checklist

• Unit tests added/updated
• API types registered with the scheme
• Validation rules included
• Docs included (not user-facing)

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[Haseebx162006]

Closing this PR because the OptimizationJob API types have already been implemented upstream in #3552.

My PR is therefore redundant. I’ll look for an open follow-up task under KEP-3562 where I can contribute further.