[core][autoscaler] Add Pod names to the output of ray status -v

[kevin85421]

Why are these changes needed?

1. Currently, the output of ray status -v only includes information on node types (i.e., group names in KubeRay) and Ray node IDs. However, it is not easy to map a Ray node ID to the name of the corresponding Ray Pod (i.e. instance id in Autoscaler).

2. Refactor

Related issue number

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[kevin85421]

cc @ryanaoleary I refactored this function a bit:

1. Avoid passing the whole ClusterStatus to the function to make it more unit testable.
2. It's not necessary to pass verbose into this function.
3. Rename dictionaries to ....to.....

[kevin85421]

cc @ryanaoleary @rueian for review