Detailed check for health check endpoint '/readyz'

/kind feature

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On #1934, we issue there might need to determine whether the katib controller is ready or not more sophistically.
But, for now, I don't have any idea for what we need to check necessary, and how often we need to check it.

Ref)
- https://github.com/kubeflow/katib/pull/1934#discussion_r950802719
- https://github.com/kubeflow/katib/pull/1934#discussion_r950828379

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