text: Title: [SDK] Support Docker image as objective in the `tune` API
  Body: Ref discussion: https://github.com/kubeflow/website/pull/3723#discussion_r1590261777.
  
  Currently, user can only pass the training function as [objective in the `tune` API](https://github.com/kubeflow/katib/blob/af900202c67843650d80ff955e4e7fb7510cc68a/sdk/python/v1beta1/kubeflow/katib/api/katib_client.py#L156) in Katib Python SDK.
  
  Similar to [`create_job` API in Training Python SDK](https://github.com/kubeflow/training-operator/blob/f23c5c8b0c87d93f61b539015883152a0872124f/sdk/python/kubeflow/training/api/training_client.py#L327), we should give user an ability to set objective as Docker image.
  
  /area sdk
  /good-first-issue
  