[Serve] serve build option to output Kubernetes config format

[shrekris-anyscale]

Description

serve build should have an option to output the config file in Kubernetes format.

Use case

serve build outputs a Serve config file that can be deployed to a Ray cluster with serve run and serve deploy:

import_path: ...

runtime_env: ...

deployments:

    - name: ...
      num_replicas: ...
      ...

    - name:
      ...

    ...

Kuberay RayServices use this config when deploying Serve. However, the KubeRay config uses camel case (see example) for the deployment options, so this config can't be directly copy-pasted.

Adding a Kubernetes output option would let users copy-paste the config directly.